express-debug-panel npm, a package manager for the JavaScript programming language, is the world's largest software registry. It contains over 1.3 million code packages as of July 2020. The registry is used to share open-source software. Finite Wisdom has contributed a code package named express-debug-panel. You can learn about it here, and see it in action below.

function next(err) {
    var layerError = err === 'route'
      ? null
      : err;

    // remove added slash
    if (slashAdded) {
      req.url = req.url.substr(1);
      slashAdded = false;
    }

    // restore altered req.url
    if (removed.length !== 0) {
      req.baseUrl = parentUrl;
      req.url = protohost + removed + req.url.substr(protohost.length);
      removed = '';
    }

    // signal to exit router
    if (layerError === 'router') {
      setImmediate(done, null)
      return
    }

    // no more matching layers
    if (idx >= stack.length) {
      setImmediate(done, layerError);
      return;
    }

    // get pathname of request
    var path = getPathname(req);

    if (path == null) {
      return done(layerError);
    }

    // find next matching layer
    var layer;
    var match;
    var route;

    while (match !== true && idx < stack.length) {
      layer = stack[idx++];
      match = matchLayer(layer, path);
      route = layer.route;

      if (typeof match !== 'boolean') {
        // hold on to layerError
        layerError = layerError || match;
      }

      if (match !== true) {
        continue;
      }

      if (!route) {
        // process non-route handlers normally
        continue;
      }

      if (layerError) {
        // routes do not match with a pending error
        match = false;
        continue;
      }

      var method = req.method;
      var has_method = route._handles_method(method);

      // build up automatic options response
      if (!has_method && method === 'OPTIONS') {
        appendMethods(options, route._options());
      }

      // don't even bother matching route
      if (!has_method && method !== 'HEAD') {
        match = false;
        continue;
      }
    }

    // no match
    if (match !== true) {
      return done(layerError);
    }

    // store route for dispatch on change
    if (route) {
      req.route = route;
    }

    // Capture one-time layer values
    req.params = self.mergeParams
      ? mergeParams(layer.params, parentParams)
      : layer.params;
    var layerPath = layer.path;

    // this should be done for the layer
    self.process_params(layer, paramcalled, req, res, function (err) {
      if (err) {
        return next(layerError || err);
      }

      if (route) {
        return layer.handle_request(req, res, next);
      }

      trim_prefix(layer, layerError, layerPath, path);
    });
  }

function () { [native code] }

function end(chunk, encoding) {
      if (ended) {
        return false;
      }

      ended = true;

      var ret;
      var sync = true;

      function writeend() {
        if (sync) {
          ret = _end.call(res, chunk, encoding);
          sync = false;
          return;
        }

        _end.call(res);
      }

      function writetop() {
        if (!sync) {
          return ret;
        }

        if (chunk == null) {
          ret = true;
          return ret;
        }

        var contentLength = Number(res.getHeader('Content-Length'));

        if (!isNaN(contentLength) && contentLength > 0) {
          // measure chunk
          chunk = !Buffer.isBuffer(chunk)
            ? Buffer.from(chunk, encoding)
            : chunk;
          encoding = undefined;

          if (chunk.length !== 0) {
            debug('split response');
            ret = _write.call(res, chunk.slice(0, chunk.length - 1));
            chunk = chunk.slice(chunk.length - 1, chunk.length);
            return ret;
          }
        }

        ret = _write.call(res, chunk, encoding);
        sync = false;

        return ret;
      }

      if (shouldDestroy(req)) {
        // destroy session
        debug('destroying');
        store.destroy(req.sessionID, function ondestroy(err) {
          if (err) {
            defer(next, err);
          }

          debug('destroyed');
          writeend();
        });

        return writetop();
      }

      // no session to save
      if (!req.session) {
        debug('no session');
        return _end.call(res, chunk, encoding);
      }

      if (!touched) {
        // touch session
        req.session.touch()
        touched = true
      }

      if (shouldSave(req)) {
        req.session.save(function onsave(err) {
          if (err) {
            defer(next, err);
          }

          writeend();
        });

        return writetop();
      } else if (storeImplementsTouch && shouldTouch(req)) {
        // store implements touch method
        debug('touching');
        store.touch(req.sessionID, req.session, function ontouch(err) {
          if (err) {
            defer(next, err);
          }

          debug('touched');
          writeend();
        });

        return writetop();
      }

      return _end.call(res, chunk, encoding);
    }

function writeHead (statusCode) {
    // set headers from arguments
    var args = setWriteHeadHeaders.apply(this, arguments)

    // fire listener
    if (!fired) {
      fired = true
      listener.call(this)

      // pass-along an updated status code
      if (typeof args[0] === 'number' && this.statusCode !== args[0]) {
        args[0] = this.statusCode
        args.length = 1
      }
    }

    return prevWriteHead.apply(this, args)
  }

function _debugEnd() { [native code] }

function _debugProcess() { [native code] }

function() {
    assert(this.channel);

    // This marks the fact that the channel is actually disconnected.
    this.channel = null;
    this[kChannelHandle] = null;

    if (this._pendingMessage)
      closePendingHandle(this);

    let fired = false;
    function finish() {
      if (fired) return;
      fired = true;

      channel.close();
      target.emit('disconnect');
    }

    // If a message is being read, then wait for it to complete.
    if (channel.buffering) {
      this.once('message', finish);
      this.once('internalMessage', finish);

      return;
    }

    process.nextTick(finish);
  }

(er, fromPromise) => {
    // It's possible that defaultTriggerAsyncId was set for a constructor
    // call that threw and was never cleared. So clear it now.
    clearDefaultTriggerAsyncId();

    // If diagnostic reporting is enabled, call into its handler to see
    // whether it is interested in handling the situation.
    // Ignore if the error is scoped inside a domain.
    // use == in the checks as we want to allow for null and undefined
    if (er == null || er.domain == null) {
      try {
        const report = internalBinding('report');
        if (report != null && report.shouldReportOnUncaughtException()) {
          report.writeReport(
            typeof er?.message === 'string' ?
              er.message :
              'Exception',
            'Exception',
            null,
            er ?? {});
        }
      } catch {}  // Ignore the exception. Diagnostic reporting is unavailable.
    }

    const type = fromPromise ? 'unhandledRejection' : 'uncaughtException';
    process.emit('uncaughtExceptionMonitor', er, type);
    if (exceptionHandlerState.captureFn !== null) {
      exceptionHandlerState.captureFn(er);
    } else if (!process.emit('uncaughtException', er, type)) {
      // If someone handled it, then great. Otherwise, die in C++ land
      // since that means that we'll exit the process, emit the 'exit' event.
      try {
        if (!process._exiting) {
          process._exiting = true;
          process.exitCode = 1;
          process.emit('exit', 1);
        }
      } catch {
        // Nothing to be done about it at this point.
      }
      return false;
    }

    // If we handled an error, then make sure any ticks get processed
    // by ensuring that the next Immediate cycle isn't empty.
    require('timers').setImmediate(noop);

    // Emit the after() hooks now that the exception has been handled.
    if (afterHooksExist()) {
      do {
        emitAfter(executionAsyncId());
      } while (hasAsyncIdStack());
    }
    // And completely empty the id stack, including anything that may be
    // cached on the native side.
    clearAsyncIdStack();

    return true;
  }

function _getActiveHandles() { [native code] }

function _getActiveRequests() { [native code] }

function _kill() { [native code] }

function _linkedBinding(module) {
    module = String(module);
    let mod = bindingObj[module];
    if (typeof mod !== 'object')
      mod = bindingObj[module] = getLinkedBinding(module);
    return mod;
  }

function _rawDebug(...args) {
    binding._rawDebug(ReflectApply(format, null, args));
  }

function(message, handle, options, callback) {
    assert(this.connected || this.channel);

    if (message === undefined)
      throw new ERR_MISSING_ARGS('message');

    // Non-serializable messages should not reach the remote
    // end point; as any failure in the stringification there
    // will result in error message that is weakly consumable.
    // So perform a final check on message prior to sending.
    if (typeof message !== 'string' &&
        typeof message !== 'object' &&
        typeof message !== 'number' &&
        typeof message !== 'boolean') {
      throw new ERR_INVALID_ARG_TYPE(
        'message', ['string', 'object', 'number', 'boolean'], message);
    }

    // Support legacy function signature
    if (typeof options === 'boolean') {
      options = { swallowErrors: options };
    }

    let obj;

    // Package messages with a handle object
    if (handle) {
      // This message will be handled by an internalMessage event handler
      message = {
        cmd: 'NODE_HANDLE',
        type: null,
        msg: message
      };

      if (handle instanceof net.Socket) {
        message.type = 'net.Socket';
      } else if (handle instanceof net.Server) {
        message.type = 'net.Server';
      } else if (handle instanceof TCP || handle instanceof Pipe) {
        message.type = 'net.Native';
      } else if (handle instanceof dgram.Socket) {
        message.type = 'dgram.Socket';
      } else if (handle instanceof UDP) {
        message.type = 'dgram.Native';
      } else {
        throw new ERR_INVALID_HANDLE_TYPE();
      }

      // Queue-up message and handle if we haven't received ACK yet.
      if (this._handleQueue) {
        ArrayPrototypePush(this._handleQueue, {
          callback: callback,
          handle: handle,
          options: options,
          message: message.msg,
        });
        return this._handleQueue.length === 1;
      }

      obj = handleConversion[message.type];

      // convert TCP object to native handle object
      handle = ReflectApply(handleConversion[message.type].send,
                            target, [message, handle, options]);

      // If handle was sent twice, or it is impossible to get native handle
      // out of it - just send a text without the handle.
      if (!handle)
        message = message.msg;

      // Update simultaneous accepts on Windows
      if (obj.simultaneousAccepts && process.platform === 'win32') {
        handle.setSimultaneousAccepts(true);
      }
    } else if (this._handleQueue &&
               !(message && (message.cmd === 'NODE_HANDLE_ACK' ||
                             message.cmd === 'NODE_HANDLE_NACK'))) {
      // Queue request anyway to avoid out-of-order messages.
      ArrayPrototypePush(this._handleQueue, {
        callback: callback,
        handle: null,
        options: options,
        message: message,
      });
      return this._handleQueue.length === 1;
    }

    const req = new WriteWrap();

    const err = writeChannelMessage(channel, req, message, handle);
    const wasAsyncWrite = streamBaseState[kLastWriteWasAsync];

    if (err === 0) {
      if (handle) {
        if (!this._handleQueue)
          this._handleQueue = [];
        if (obj && obj.postSend)
          obj.postSend(message, handle, options, callback, target);
      }

      if (wasAsyncWrite) {
        req.oncomplete = () => {
          control.unrefCounted();
          if (typeof callback === 'function')
            callback(null);
        };
        control.refCounted();
      } else if (typeof callback === 'function') {
        process.nextTick(callback, null);
      }
    } else {
      // Cleanup handle on error
      if (obj && obj.postSend)
        obj.postSend(message, handle, options, callback);

      if (!options.swallowErrors) {
        const ex = errnoException(err, 'write');
        if (typeof callback === 'function') {
          process.nextTick(callback, ex);
        } else {
          process.nextTick(() => this.emit('error', ex));
        }
      }
    }

    /* If the primary is > 2 read() calls behind, please stop sending. */
    return channel.writeQueueSize < (65536 * 2);
  }

() => {}

() => {}

function runNextTicks() {
  if (!hasTickScheduled() && !hasRejectionToWarn())
    runMicrotasks();
  if (!hasTickScheduled() && !hasRejectionToWarn())
    return;

  processTicksAndRejections();
}

function abort() { [native code] }

function deprecated(...args) {
    if (!warned) {
      warned = true;
      if (code !== undefined) {
        if (!codesWarned.has(code)) {
          process.emitWarning(msg, 'DeprecationWarning', code, deprecated);
          codesWarned.add(code);
        }
      } else {
        process.emitWarning(msg, 'DeprecationWarning', deprecated);
      }
    }
    if (new.target) {
      return ReflectConstruct(fn, args, new.target);
    }
    return ReflectApply(fn, this, args);
  }

function binding(module) {
    module = String(module);
    // Deprecated specific process.binding() modules, but not all, allow
    // selective fallback to internalBinding for the deprecated ones.
    if (internalBindingAllowlist.has(module)) {
      if (runtimeDeprecatedList.has(module)) {
        runtimeDeprecatedList.delete(module);
        process.emitWarning(
          `Access to process.binding('${module}') is deprecated.`,
          'DeprecationWarning',
          'DEP0111');
      }
      if (legacyWrapperList.has(module)) {
        return nativeModuleRequire('internal/legacy/processbinding')[module]();
      }
      return internalBinding(module);
    }
    // eslint-disable-next-line no-restricted-syntax
    throw new Error(`No such module: ${module}`);
  }

function wrappedChdir(directory) {
  validateString(directory, 'directory');
  rawMethods.chdir(directory);
  // Mark cache that it requires an update.
  cachedCwd = '';
}

function cpuUsage(prevValue) {
    // If a previous value was passed in, ensure it has the correct shape.
    if (prevValue) {
      if (!previousValueIsValid(prevValue.user)) {
        validateObject(prevValue, 'prevValue');

        validateNumber(prevValue.user, 'prevValue.user');
        throw new ERR_INVALID_ARG_VALUE.RangeError('prevValue.user',
                                                   prevValue.user);
      }

      if (!previousValueIsValid(prevValue.system)) {
        validateNumber(prevValue.system, 'prevValue.system');
        throw new ERR_INVALID_ARG_VALUE.RangeError('prevValue.system',
                                                   prevValue.system);
      }
    }

    // Call the native function to get the current values.
    _cpuUsage(cpuValues);

    // If a previous value was passed in, return diff of current from previous.
    if (prevValue) {
      return {
        user: cpuValues[0] - prevValue.user,
        system: cpuValues[1] - prevValue.system
      };
    }

    // If no previous value passed in, return current value.
    return {
      user: cpuValues[0],
      system: cpuValues[1]
    };
  }

function wrappedCwd() {
  if (cachedCwd === '')
    cachedCwd = rawMethods.cwd();
  return cachedCwd;
}

function() {
    if (!this.connected) {
      this.emit('error', new ERR_IPC_DISCONNECTED());
      return;
    }

    // Do not allow any new messages to be written.
    this.connected = false;

    // If there are no queued messages, disconnect immediately. Otherwise,
    // postpone the disconnect so that it happens internally after the
    // queue is flushed.
    if (!this._handleQueue)
      this._disconnect();
  }

function dlopen() { [native code] }

function emitWarning(warning, type, code, ctor) {
  let detail;
  if (type !== null && typeof type === 'object' && !ArrayIsArray(type)) {
    ctor = type.ctor;
    code = type.code;
    if (typeof type.detail === 'string')
      detail = type.detail;
    type = type.type || 'Warning';
  } else if (typeof type === 'function') {
    ctor = type;
    code = undefined;
    type = 'Warning';
  }
  if (type !== undefined)
    validateString(type, 'type');
  if (typeof code === 'function') {
    ctor = code;
    code = undefined;
  } else if (code !== undefined) {
    validateString(code, 'code');
  }
  if (typeof warning === 'string') {
    warning = createWarningObject(warning, type, code, ctor, detail);
  } else if (!(warning instanceof Error)) {
    throw new ERR_INVALID_ARG_TYPE('warning', ['Error', 'string'], warning);
  }
  if (warning.name === 'DeprecationWarning') {
    if (process.noDeprecation)
      return;
    if (process.throwDeprecation) {
      // Delay throwing the error to guarantee that all former warnings were
      // properly logged.
      return process.nextTick(() => {
        throw warning;
      });
    }
  }
  process.nextTick(doEmitWarning, warning);
}

function exit(code) {
    if (code || code === 0)
      process.exitCode = code;

    if (!process._exiting) {
      process._exiting = true;
      process.emit('exit', process.exitCode || 0);
    }
    // FIXME(joyeecheung): This is an undocumented API that gets monkey-patched
    // in the user land. Either document it, or deprecate it in favor of a
    // better public alternative.
    process.reallyExit(process.exitCode || 0);
  }

function getegid() { [native code] }

function geteuid() { [native code] }

function getgid() { [native code] }

function getgroups() { [native code] }

function getuid() { [native code] }

function hasUncaughtExceptionCaptureCallback() {
  return exceptionHandlerState.captureFn !== null;
}

function hrtime(time) {
    _hrtime.hrtime();

    if (time !== undefined) {
      validateArray(time, 'time');
      if (time.length !== 2) {
        throw new ERR_OUT_OF_RANGE('time', 2, time.length);
      }

      const sec = (hrValues[0] * 0x100000000 + hrValues[1]) - time[0];
      const nsec = hrValues[2] - time[1];
      const needsBorrow = nsec < 0;
      return [needsBorrow ? sec - 1 : sec, needsBorrow ? nsec + 1e9 : nsec];
    }

    return [
      hrValues[0] * 0x100000000 + hrValues[1],
      hrValues[2],
    ];
  }

function initgroups(user, extraGroup) {
    validateId(user, 'user');
    validateId(extraGroup, 'extraGroup');
    // Result is 0 on success, 1 if user is unknown, 2 if group is unknown.
    const result = _initgroups(user, extraGroup);
    if (result === 1) {
      throw new ERR_UNKNOWN_CREDENTIAL('User', user);
    } else if (result === 2) {
      throw new ERR_UNKNOWN_CREDENTIAL('Group', extraGroup);
    }
  }

function kill(pid, sig) {
    let err;

    // eslint-disable-next-line eqeqeq
    if (pid != (pid | 0)) {
      throw new ERR_INVALID_ARG_TYPE('pid', 'number', pid);
    }

    // Preserve null signal
    if (sig === (sig | 0)) {
      // XXX(joyeecheung): we have to use process._kill here because
      // it's monkey-patched by tests.
      err = process._kill(pid, sig);
    } else {
      sig = sig || 'SIGTERM';
      if (constants[sig]) {
        err = process._kill(pid, constants[sig]);
      } else {
        throw new ERR_UNKNOWN_SIGNAL(sig);
      }
    }

    if (err)
      throw errnoException(err, 'kill');

    return true;
  }

function memoryUsage() {
    _memoryUsage(memValues);
    return {
      rss: memValues[0],
      heapTotal: memValues[1],
      heapUsed: memValues[2],
      external: memValues[3],
      arrayBuffers: memValues[4]
    };
  }

function nextTick(callback) {
  validateCallback(callback);

  if (process._exiting)
    return;

  let args;
  switch (arguments.length) {
    case 1: break;
    case 2: args = [arguments[1]]; break;
    case 3: args = [arguments[1], arguments[2]]; break;
    case 4: args = [arguments[1], arguments[2], arguments[3]]; break;
    default:
      args = new Array(arguments.length - 1);
      for (let i = 1; i < arguments.length; i++)
        args[i - 1] = arguments[i];
  }

  if (queue.isEmpty())
    setHasTickScheduled(true);
  const asyncId = newAsyncId();
  const triggerAsyncId = getDefaultTriggerAsyncId();
  const tickObject = {
    [async_id_symbol]: asyncId,
    [trigger_async_id_symbol]: triggerAsyncId,
    callback,
    args
  };
  if (initHooksExist())
    emitInit(asyncId, 'TickObject', triggerAsyncId, tickObject);
  queue.push(tickObject);
}

function() {
    process.stdin.resume();
    return process.stdin;
  }

function reallyExit() { [native code] }

function resourceUsage() {
    _resourceUsage(resourceValues);
    return {
      userCPUTime: resourceValues[0],
      systemCPUTime: resourceValues[1],
      maxRSS: resourceValues[2],
      sharedMemorySize: resourceValues[3],
      unsharedDataSize: resourceValues[4],
      unsharedStackSize: resourceValues[5],
      minorPageFault: resourceValues[6],
      majorPageFault: resourceValues[7],
      swappedOut: resourceValues[8],
      fsRead: resourceValues[9],
      fsWrite: resourceValues[10],
      ipcSent: resourceValues[11],
      ipcReceived: resourceValues[12],
      signalsCount: resourceValues[13],
      voluntaryContextSwitches: resourceValues[14],
      involuntaryContextSwitches: resourceValues[15]
    };
  }

function(message, handle, options, callback) {
    if (typeof handle === 'function') {
      callback = handle;
      handle = undefined;
      options = undefined;
    } else if (typeof options === 'function') {
      callback = options;
      options = undefined;
    } else if (options !== undefined) {
      validateObject(options, 'options');
    }

    options = { swallowErrors: false, ...options };

    if (this.connected) {
      return this._send(message, handle, options, callback);
    }
    const ex = new ERR_IPC_CHANNEL_CLOSED();
    if (typeof callback === 'function') {
      process.nextTick(callback, ex);
    } else {
      process.nextTick(() => this.emit('error', ex));
    }
    return false;
  }

function setSourceMapsEnabled(val) {
  validateBoolean(val, 'val');

  const {
    setSourceMapsEnabled,
    setPrepareStackTraceCallback
  } = internalBinding('errors');
  setSourceMapsEnabled(val);
  if (val) {
    const {
      prepareStackTrace
    } = require('internal/source_map/prepare_stack_trace');
    setPrepareStackTraceCallback(prepareStackTrace);
  } else if (sourceMapsEnabled !== undefined) {
    // Reset prepare stack trace callback only when disabling source maps.
    const {
      prepareStackTrace,
    } = require('internal/errors');
    setPrepareStackTraceCallback(prepareStackTrace);
  }

  sourceMapsEnabled = val;
}

function setUncaughtExceptionCaptureCallback(fn) {
  if (fn === null) {
    exceptionHandlerState.captureFn = fn;
    shouldAbortOnUncaughtToggle[0] = 1;
    process.report.reportOnUncaughtException = exceptionHandlerState.reportFlag;
    return;
  }
  if (typeof fn !== 'function') {
    throw new ERR_INVALID_ARG_TYPE('fn', ['Function', 'null'], fn);
  }
  if (exceptionHandlerState.captureFn !== null) {
    throw new ERR_UNCAUGHT_EXCEPTION_CAPTURE_ALREADY_SET();
  }
  exceptionHandlerState.captureFn = fn;
  shouldAbortOnUncaughtToggle[0] = 0;
  exceptionHandlerState.reportFlag =
    process.report.reportOnUncaughtException === true;
  process.report.reportOnUncaughtException = false;
}

function(id) {
      validateId(id, 'id');
      if (typeof id === 'number') id |= 0;
      // Result is 0 on success, 1 if credential is unknown.
      const result = method(id);
      if (result === 1) {
        throw new ERR_UNKNOWN_CREDENTIAL(type, id);
      }
    }

function(id) {
      validateId(id, 'id');
      if (typeof id === 'number') id |= 0;
      // Result is 0 on success, 1 if credential is unknown.
      const result = method(id);
      if (result === 1) {
        throw new ERR_UNKNOWN_CREDENTIAL(type, id);
      }
    }

function(id) {
      validateId(id, 'id');
      if (typeof id === 'number') id |= 0;
      // Result is 0 on success, 1 if credential is unknown.
      const result = method(id);
      if (result === 1) {
        throw new ERR_UNKNOWN_CREDENTIAL(type, id);
      }
    }

function setgroups(groups) {
    validateArray(groups, 'groups');
    for (let i = 0; i < groups.length; i++) {
      validateId(groups[i], `groups[${i}]`);
    }
    // Result is 0 on success. A positive integer indicates that the
    // corresponding group was not found.
    const result = _setgroups(groups);
    if (result > 0) {
      throw new ERR_UNKNOWN_CREDENTIAL('Group', groups[result - 1]);
    }
  }

function(id) {
      validateId(id, 'id');
      if (typeof id === 'number') id |= 0;
      // Result is 0 on success, 1 if credential is unknown.
      const result = method(id);
      if (result === 1) {
        throw new ERR_UNKNOWN_CREDENTIAL(type, id);
      }
    }

function wrappedUmask(mask) {
  if (mask !== undefined) {
    mask = parseFileMode(mask, 'mask');
  }
  return rawMethods.umask(mask);
}

function uptime() { [native code] }

function router(req, res, next) {
    router.handle(req, res, next);
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function addListener(type, listener) {
  return _addListener(this, type, listener, false);
}

function all(path) {
  this.lazyrouter();

  var route = this._router.route(path);
  var args = slice.call(arguments, 1);

  for (var i = 0; i < methods.length; i++) {
    route[methods[i]].apply(route, args);
  }

  return this;
}

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function defaultConfiguration() {
  var env = process.env.NODE_ENV || 'development';

  // default settings
  this.enable('x-powered-by');
  this.set('etag', 'weak');
  this.set('env', env);
  this.set('query parser', 'extended');
  this.set('subdomain offset', 2);
  this.set('trust proxy', false);

  // trust proxy inherit back-compat
  Object.defineProperty(this.settings, trustProxyDefaultSymbol, {
    configurable: true,
    value: true
  });

  debug('booting in %s mode', env);

  this.on('mount', function onmount(parent) {
    // inherit trust proxy
    if (this.settings[trustProxyDefaultSymbol] === true
      && typeof parent.settings['trust proxy fn'] === 'function') {
      delete this.settings['trust proxy'];
      delete this.settings['trust proxy fn'];
    }

    // inherit protos
    setPrototypeOf(this.request, parent.request)
    setPrototypeOf(this.response, parent.response)
    setPrototypeOf(this.engines, parent.engines)
    setPrototypeOf(this.settings, parent.settings)
  });

  // setup locals
  this.locals = Object.create(null);

  // top-most app is mounted at /
  this.mountpath = '/';

  // default locals
  this.locals.settings = this.settings;

  // default configuration
  this.set('view', View);
  this.set('views', resolve('views'));
  this.set('jsonp callback name', 'callback');

  if (env === 'production') {
    this.enable('view cache');
  }

  Object.defineProperty(this, 'router', {
    get: function() {
      throw new Error('\'app.router\' is deprecated!\nPlease see the 3.x to 4.x migration guide for details on how to update your app.');
    }
  });
}

function (arg0) {
"use strict"
log.call(deprecate, message, site)
return fn.apply(this, arguments)
}

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function disable(setting) {
  return this.set(setting, false);
}

function disabled(setting) {
  return !this.set(setting);
}

function emit(type, ...args) {
  let doError = (type === 'error');

  const events = this._events;
  if (events !== undefined) {
    if (doError && events[kErrorMonitor] !== undefined)
      this.emit(kErrorMonitor, ...args);
    doError = (doError && events.error === undefined);
  } else if (!doError)
    return false;

  // If there is no 'error' event listener then throw.
  if (doError) {
    let er;
    if (args.length > 0)
      er = args[0];
    if (er instanceof Error) {
      try {
        const capture = {};
        ErrorCaptureStackTrace(capture, EventEmitter.prototype.emit);
        ObjectDefineProperty(er, kEnhanceStackBeforeInspector, {
          value: FunctionPrototypeBind(enhanceStackTrace, this, er, capture),
          configurable: true
        });
      } catch {}

      // Note: The comments on the `throw` lines are intentional, they show
      // up in Node's output if this results in an unhandled exception.
      throw er; // Unhandled 'error' event
    }

    let stringifiedEr;
    try {
      stringifiedEr = inspect(er);
    } catch {
      stringifiedEr = er;
    }

    // At least give some kind of context to the user
    const err = new ERR_UNHANDLED_ERROR(stringifiedEr);
    err.context = er;
    throw err; // Unhandled 'error' event
  }

  const handler = events[type];

  if (handler === undefined)
    return false;

  if (typeof handler === 'function') {
    const result = handler.apply(this, args);

    // We check if result is undefined first because that
    // is the most common case so we do not pay any perf
    // penalty
    if (result !== undefined && result !== null) {
      addCatch(this, result, type, args);
    }
  } else {
    const len = handler.length;
    const listeners = arrayClone(handler);
    for (let i = 0; i < len; ++i) {
      const result = listeners[i].apply(this, args);

      // We check if result is undefined first because that
      // is the most common case so we do not pay any perf
      // penalty.
      // This code is duplicated because extracting it away
      // would make it non-inlineable.
      if (result !== undefined && result !== null) {
        addCatch(this, result, type, args);
      }
    }
  }

  return true;
}

function enable(setting) {
  return this.set(setting, true);
}

function enabled(setting) {
  return Boolean(this.set(setting));
}

function engine(ext, fn) {
  if (typeof fn !== 'function') {
    throw new Error('callback function required');
  }

  // get file extension
  var extension = ext[0] !== '.'
    ? '.' + ext
    : ext;

  // store engine
  this.engines[extension] = fn;

  return this;
}

function eventNames() {
  return this._eventsCount > 0 ? ReflectOwnKeys(this._events) : [];
}

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function getMaxListeners() {
  return _getMaxListeners(this);
}

function handle(req, res, callback) {
  var router = this._router;

  // final handler
  var done = callback || finalhandler(req, res, {
    env: this.get('env'),
    onerror: logerror.bind(this)
  });

  // no routes
  if (!router) {
    debug('no routes defined on app');
    done();
    return;
  }

  router.handle(req, res, done);
}

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function init() {
  this.cache = {};
  this.engines = {};
  this.settings = {};

  this.defaultConfiguration();
}

function lazyrouter() {
  if (!this._router) {
    this._router = new Router({
      caseSensitive: this.enabled('case sensitive routing'),
      strict: this.enabled('strict routing')
    });

    this._router.use(query(this.get('query parser fn')));
    this._router.use(middleware.init(this));
  }
}

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function listen() {
  var server = http.createServer(this);
  return server.listen.apply(server, arguments);
}

function listenerCount(type) {
  const events = this._events;

  if (events !== undefined) {
    const evlistener = events[type];

    if (typeof evlistener === 'function') {
      return 1;
    } else if (evlistener !== undefined) {
      return evlistener.length;
    }
  }

  return 0;
}

function listeners(type) {
  return _listeners(this, type, true);
}

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function removeListener(type, listener) {
      checkListener(listener);

      const events = this._events;
      if (events === undefined)
        return this;

      const list = events[type];
      if (list === undefined)
        return this;

      if (list === listener || list.listener === listener) {
        if (--this._eventsCount === 0)
          this._events = ObjectCreate(null);
        else {
          delete events[type];
          if (events.removeListener)
            this.emit('removeListener', type, list.listener || listener);
        }
      } else if (typeof list !== 'function') {
        let position = -1;

        for (let i = list.length - 1; i >= 0; i--) {
          if (list[i] === listener || list[i].listener === listener) {
            position = i;
            break;
          }
        }

        if (position < 0)
          return this;

        if (position === 0)
          list.shift();
        else {
          if (spliceOne === undefined)
            spliceOne = require('internal/util').spliceOne;
          spliceOne(list, position);
        }

        if (list.length === 1)
          events[type] = list[0];

        if (events.removeListener !== undefined)
          this.emit('removeListener', type, listener);
      }

      return this;
    }

function addListener(type, listener) {
  return _addListener(this, type, listener, false);
}

function once(type, listener) {
  checkListener(listener);

  this.on(type, _onceWrap(this, type, listener));
  return this;
}

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function param(name, fn) {
  this.lazyrouter();

  if (Array.isArray(name)) {
    for (var i = 0; i < name.length; i++) {
      this.param(name[i], fn);
    }

    return this;
  }

  this._router.param(name, fn);

  return this;
}

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function path() {
  return this.parent
    ? this.parent.path() + this.mountpath
    : '';
}

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function prependListener(type, listener) {
      return _addListener(this, type, listener, true);
    }

function prependOnceListener(type, listener) {
      checkListener(listener);

      this.prependListener(type, _onceWrap(this, type, listener));
      return this;
    }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function rawListeners(type) {
  return _listeners(this, type, false);
}

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function removeAllListeners(type) {
      const events = this._events;
      if (events === undefined)
        return this;

      // Not listening for removeListener, no need to emit
      if (events.removeListener === undefined) {
        if (arguments.length === 0) {
          this._events = ObjectCreate(null);
          this._eventsCount = 0;
        } else if (events[type] !== undefined) {
          if (--this._eventsCount === 0)
            this._events = ObjectCreate(null);
          else
            delete events[type];
        }
        return this;
      }

      // Emit removeListener for all listeners on all events
      if (arguments.length === 0) {
        for (const key of ReflectOwnKeys(events)) {
          if (key === 'removeListener') continue;
          this.removeAllListeners(key);
        }
        this.removeAllListeners('removeListener');
        this._events = ObjectCreate(null);
        this._eventsCount = 0;
        return this;
      }

      const listeners = events[type];

      if (typeof listeners === 'function') {
        this.removeListener(type, listeners);
      } else if (listeners !== undefined) {
        // LIFO order
        for (let i = listeners.length - 1; i >= 0; i--) {
          this.removeListener(type, listeners[i]);
        }
      }

      return this;
    }

function removeListener(type, listener) {
      checkListener(listener);

      const events = this._events;
      if (events === undefined)
        return this;

      const list = events[type];
      if (list === undefined)
        return this;

      if (list === listener || list.listener === listener) {
        if (--this._eventsCount === 0)
          this._events = ObjectCreate(null);
        else {
          delete events[type];
          if (events.removeListener)
            this.emit('removeListener', type, list.listener || listener);
        }
      } else if (typeof list !== 'function') {
        let position = -1;

        for (let i = list.length - 1; i >= 0; i--) {
          if (list[i] === listener || list[i].listener === listener) {
            position = i;
            break;
          }
        }

        if (position < 0)
          return this;

        if (position === 0)
          list.shift();
        else {
          if (spliceOne === undefined)
            spliceOne = require('internal/util').spliceOne;
          spliceOne(list, position);
        }

        if (list.length === 1)
          events[type] = list[0];

        if (events.removeListener !== undefined)
          this.emit('removeListener', type, listener);
      }

      return this;
    }

function render(name, options, callback) {
  var cache = this.cache;
  var done = callback;
  var engines = this.engines;
  var opts = options;
  var renderOptions = {};
  var view;

  // support callback function as second arg
  if (typeof options === 'function') {
    done = options;
    opts = {};
  }

  // merge app.locals
  merge(renderOptions, this.locals);

  // merge options._locals
  if (opts._locals) {
    merge(renderOptions, opts._locals);
  }

  // merge options
  merge(renderOptions, opts);

  // set .cache unless explicitly provided
  if (renderOptions.cache == null) {
    renderOptions.cache = this.enabled('view cache');
  }

  // primed cache
  if (renderOptions.cache) {
    view = cache[name];
  }

  // view
  if (!view) {
    var View = this.get('view');

    view = new View(name, {
      defaultEngine: this.get('view engine'),
      root: this.get('views'),
      engines: engines
    });

    if (!view.path) {
      var dirs = Array.isArray(view.root) && view.root.length > 1
        ? 'directories "' + view.root.slice(0, -1).join('", "') + '" or "' + view.root[view.root.length - 1] + '"'
        : 'directory "' + view.root + '"'
      var err = new Error('Failed to lookup view "' + name + '" in views ' + dirs);
      err.view = view;
      return done(err);
    }

    // prime the cache
    if (renderOptions.cache) {
      cache[name] = view;
    }
  }

  // render
  tryRender(view, renderOptions, done);
}

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function route(path) {
  this.lazyrouter();
  return this._router.route(path);
}

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function set(setting, val) {
  if (arguments.length === 1) {
    // app.get(setting)
    return this.settings[setting];
  }

  debug('set "%s" to %o', setting, val);

  // set value
  this.settings[setting] = val;

  // trigger matched settings
  switch (setting) {
    case 'etag':
      this.set('etag fn', compileETag(val));
      break;
    case 'query parser':
      this.set('query parser fn', compileQueryParser(val));
      break;
    case 'trust proxy':
      this.set('trust proxy fn', compileTrust(val));

      // trust proxy inherit back-compat
      Object.defineProperty(this.settings, trustProxyDefaultSymbol, {
        configurable: true,
        value: false
      });

      break;
  }

  return this;
}

function setMaxListeners(n) {
  if (typeof n !== 'number' || n < 0 || NumberIsNaN(n)) {
    throw new ERR_OUT_OF_RANGE('n', 'a non-negative number', n);
  }
  this._maxListeners = n;
  return this;
}

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function(path){
    if (method === 'get' && arguments.length === 1) {
      // app.get(setting)
      return this.set(path);
    }

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, slice.call(arguments, 1));
    return this;
  }

function use(fn) {
  var offset = 0;
  var path = '/';

  // default path to '/'
  // disambiguate app.use([fn])
  if (typeof fn !== 'function') {
    var arg = fn;

    while (Array.isArray(arg) && arg.length !== 0) {
      arg = arg[0];
    }

    // first arg is the path
    if (typeof arg !== 'function') {
      offset = 1;
      path = fn;
    }
  }

  var fns = flatten(slice.call(arguments, offset));

  if (fns.length === 0) {
    throw new TypeError('app.use() requires a middleware function')
  }

  // setup router
  this.lazyrouter();
  var router = this._router;

  fns.forEach(function (fn) {
    // non-express app
    if (!fn || !fn.handle || !fn.set) {
      return router.use(path, fn);
    }

    debug('.use app under %s', path);
    fn.mountpath = path;
    fn.parent = this;

    // restore .app property on req and res
    router.use(path, function mounted_app(req, res, next) {
      var orig = req.app;
      fn.handle(req, res, function (err) {
        setPrototypeOf(req, orig.request)
        setPrototypeOf(res, orig.response)
        next(err);
      });
    });

    // mounted an app
    fn.emit('mount', this);
  }, this);

  return this;
}