refactor(middleware): update middleware/common to ES6 (#3028)

lib/middleware/common.js

@@ -1,41 +1,44 @@
 /**
  * This module contains some common helpers shared between middlewares
  */
+'use strict'
 
-var mime = require('mime')
-var _ = require('lodash')
-var parseRange = require('range-parser')
-var Buffer = require('safe-buffer').Buffer
+const mime = require('mime')
+const _ = require('lodash')
+const parseRange = require('range-parser')
+const Buffer = require('safe-buffer').Buffer
 
-var log = require('../logger').create('web-server')
+const log = require('../logger').create('web-server')
 
-var PromiseContainer = function () {
-  var promise
+class PromiseContainer {
+  constructor () {
+    this.promise = null
+  }
 
-  this.then = function (success, error) {
+  then (success, error) {
     error = error || _.noop
-    return promise.then(success).catch(error)
+    return this.promise.then(success).catch(error)
   }
 
-  this.set = function (newPromise) {
-    promise = newPromise
+  set (newPromise) {
+    this.promise = newPromise
   }
 }
 
-var serve404 = function (response, path) {
+function serve404 (response, path) {
   log.warn('404: ' + path)
   response.writeHead(404)
   return response.end('NOT FOUND')
 }
 
-var createServeFile = function (fs, directory, config) {
-  var cache = Object.create(null)
+function createServeFile (fs, directory, config) {
+  const cache = Object.create(null)
 
   return function (filepath, rangeHeader, response, transform, content, doNotCache) {
-    var responseData
+    let responseData
 
-    var convertForRangeRequest = function () {
-      var range = parseRange(responseData.length, rangeHeader)
+    const convertForRangeRequest = function () {
+      const range = parseRange(responseData.length, rangeHeader)
       if (range === -2) {
         // malformed header string
         return 200
@@ -46,8 +49,8 @@ var createServeFile = function (fs, directory, config) {
       } else if (range.type === 'bytes') {
         responseData = Buffer.from(responseData)
         if (range.length === 1) {
-          var start = range[0].start
-          var end = range[0].end
+          const start = range[0].start
+          const end = range[0].end
           response.setHeader(
             'Content-Range',
             'bytes ' + start + '-' + end + '/' + responseData.length
@@ -76,7 +79,7 @@ var createServeFile = function (fs, directory, config) {
 
     if (config && config.customHeaders && config.customHeaders.length > 0) {
       config.customHeaders.forEach(function (header) {
-        var regex = new RegExp(header.match)
+        const regex = new RegExp(header.match)
         if (regex.test(filepath)) {
           log.debug('setting header: ' + header.name + ' for: ' + filepath)
           response.setHeader(header.name, header.value)
@@ -91,12 +94,7 @@ var createServeFile = function (fs, directory, config) {
       // call custom transform fn to transform the data
       responseData = (transform && transform(content)) || content
 
-      if (rangeHeader) {
-        var code = convertForRangeRequest()
-        response.writeHead(code)
-      } else {
-        response.writeHead(200)
-      }
+      response.writeHead(rangeHeader ? convertForRangeRequest() : 200)
 
       log.debug('serving (cached): ' + filepath)
       return response.end(responseData)
@@ -116,33 +114,28 @@ var createServeFile = function (fs, directory, config) {
       // call custom transform fn to transform the data
       responseData = (transform && transform(data.toString())) || data
 
-      if (rangeHeader) {
-        var code = convertForRangeRequest()
-        response.writeHead(code)
-      } else {
-        response.writeHead(200)
-      }
+      response.writeHead(rangeHeader ? convertForRangeRequest() : 200)
 
       log.debug('serving: ' + filepath)
       return response.end(responseData)
     })
   }
 }
 
-var setNoCacheHeaders = function (response) {
+function setNoCacheHeaders (response) {
   response.setHeader('Cache-Control', 'no-cache')
   response.setHeader('Pragma', 'no-cache')
   response.setHeader('Expires', (new Date(0)).toUTCString())
 }
 
-var setHeavyCacheHeaders = function (response) {
+function setHeavyCacheHeaders (response) {
   response.setHeader('Cache-Control', 'public, max-age=31536000')
 }
 
-var initializeMimeTypes = function (config) {
+function initializeMimeTypes (config) {
   if (config && config.mime) {
     _.forEach(config.mime, function (value, key) {
-      var map = {}
+      const map = {}
       map[key] = value
       mime.define(map)
     })