diff --git a/lib/app/client.js b/lib/app/client.js
index 7c93bf133d..5f5514fbdf 100644
--- a/lib/app/client.js
+++ b/lib/app/client.js
@@ -109,7 +109,7 @@ function mapTransitions(Components, to, from) {
     if (from && from.matched.length && from.matched[0].components.default) {
       const from_transitions = componentTransitions(from.matched[0].components.default)
       Object.keys(from_transitions)
-        .filter((key) => from_transitions[key] && key.toLowerCase().indexOf('leave') !== -1)
+        .filter((key) => from_transitions[key] && key.toLowerCase().includes('leave'))
         .forEach((key) => { transitions[key] = from_transitions[key] })
     }
 
diff --git a/lib/app/components/nuxt-child.js b/lib/app/components/nuxt-child.js
index 63b43738f0..59ab308bde 100644
--- a/lib/app/components/nuxt-child.js
+++ b/lib/app/components/nuxt-child.js
@@ -23,6 +23,7 @@ export default {
         transitionProps[key] = transition[key]
       }
     })
+
     let listeners = {}
     listenersKeys.forEach((key) => {
       if (typeof transition[key] === 'function') {
@@ -30,7 +31,7 @@ export default {
       }
     })
     // Add triggerScroll event on beforeEnter (fix #1376)
-    let beforeEnter = listeners.beforeEnter
+    const beforeEnter = listeners.beforeEnter
     listeners.beforeEnter = (el) => {
       // Ensure to trigger scroll event after calling scrollBehavior
       window.<%= globals.nuxt %>.$nextTick(() => {
diff --git a/lib/app/middleware.js b/lib/app/middleware.js
index 1b728bdba6..0adfbd9e23 100644
--- a/lib/app/middleware.js
+++ b/lib/app/middleware.js
@@ -1,18 +1,16 @@
 <% if (middleware) { %>
-let files = require.context('@/<%= dir.middleware %>', false, /^\.\/(?!<%= ignorePrefix %>)[^.]+\.(<%= extensions %>)$/)
-let filenames = files.keys()
+const files = require.context('@/<%= dir.middleware %>', false, /^\.\/(?!<%= ignorePrefix %>)[^.]+\.(<%= extensions %>)$/)
+const filenames = files.keys()
 
 function getModule (filename) {
-  let file = files(filename)
-  return file.default
-    ? file.default
-    : file
+  const file = files(filename)
+  return file.default || file
 }
-let middleware = {}
+const middleware = {}
 
 // Generate the middleware
-for (let filename of filenames) {
-  let name = filename.replace(/^\.\//, '').replace(/\.(<%= extensions %>)$/, '')
+for (const filename of filenames) {
+  const name = filename.replace(/^\.\//, '').replace(/\.(<%= extensions %>)$/, '')
   middleware[name] = getModule(filename)
 }
 
diff --git a/lib/app/server.js b/lib/app/server.js
index 07630445a4..3c38315aa7 100644
--- a/lib/app/server.js
+++ b/lib/app/server.js
@@ -21,7 +21,7 @@ const createNext = (ssrContext) => (opts) => {
   }
   opts.query = stringify(opts.query)
   opts.path = opts.path + (opts.query ? '?' + opts.query : '')
-  if (opts.path.indexOf('http') !== 0 && ('<%= router.base %>' !== '/' && opts.path.indexOf('<%= router.base %>') !== 0)) {
+  if (!opts.path.startsWith('http') && ('<%= router.base %>' !== '/' && !opts.path.startsWith('<%= router.base %>'))) {
     opts.path = urlJoin('<%= router.base %>', opts.path)
   }
   // Avoid loop redirect
diff --git a/lib/app/store.js b/lib/app/store.js
index 08106ce50a..0b37aa5bc8 100644
--- a/lib/app/store.js
+++ b/lib/app/store.js
@@ -10,7 +10,7 @@ const filenames = files.keys()
 let storeData = {}
 
 // Check if {dir.store}/index.js exists
-const indexFilename = filenames.find(name => name.includes('./index.'))
+const indexFilename = filenames.find(filename => filename.includes('./index.'))
 
 if (indexFilename) {
   storeData = getModule(indexFilename)
diff --git a/lib/app/utils.js b/lib/app/utils.js
index 2b17d27387..ecc1c261cc 100644
--- a/lib/app/utils.js
+++ b/lib/app/utils.js
@@ -496,7 +496,7 @@ function formatUrl (url, query) {
   if (index !== -1) {
     protocol = url.substring(0, index)
     url = url.substring(index + 3)
-  } else if (url.indexOf('//') === 0) {
+  } else if (url.startsWith('//')) {
     url = url.substring(2)
   }
 
diff --git a/lib/builder/builder.js b/lib/builder/builder.js
index f44dcd44c8..9dc2c19604 100644
--- a/lib/builder/builder.js
+++ b/lib/builder/builder.js
@@ -318,7 +318,6 @@ export default class Builder {
       templateVars.router.routes,
       r
     )
-
     // router.extendRoutes method
     if (typeof this.options.router.extendRoutes === 'function') {
       // let the user extend the routes
@@ -349,7 +348,7 @@ export default class Builder {
     templatesFiles = templatesFiles
       .map((file) => {
         // Skip if custom file was already provided in build.templates[]
-        if (customTemplateFiles.indexOf(file) !== -1) {
+        if (customTemplateFiles.includes(file)) {
           return
         }
         // Allow override templates using a file with same name in ${srcDir}/app
diff --git a/lib/builder/generator.js b/lib/builder/generator.js
index 407ca32794..d28aaa615c 100644
--- a/lib/builder/generator.js
+++ b/lib/builder/generator.js
@@ -1,10 +1,9 @@
 import path from 'path'
-import _ from 'lodash'
 import htmlMinifier from 'html-minifier'
 import Chalk from 'chalk'
 import fsExtra from 'fs-extra'
 import consola from 'consola'
-import { flatRoutes, isUrl, promisifyRoute, waitFor } from '../common/utils'
+import { flatRoutes, isUrl, promisifyRoute, waitFor, isString } from '../common/utils'
 
 export default class Generator {
   constructor(nuxt, builder) {
@@ -187,13 +186,13 @@ export default class Generator {
     // Fill routeMap with given generate.routes
     generateRoutes.forEach((route) => {
       // route is either a string or like { route : '/my_route/1', payload: {} }
-      const path = _.isString(route) ? route : route.route
+      const path = isString(route) ? route : route.route
       routeMap[path] = {
         route: path,
         payload: route.payload || null
       }
     })
-    return _.values(routeMap)
+    return Object.values(routeMap)
   }
 
   async generateRoute({ route, payload = {}, errors = [] }) {
diff --git a/lib/builder/webpack/base.js b/lib/builder/webpack/base.js
index 6bcbd8c469..d2cfb15835 100644
--- a/lib/builder/webpack/base.js
+++ b/lib/builder/webpack/base.js
@@ -76,9 +76,9 @@ export default class WebpackBaseConfig {
       'process.mode': JSON.stringify(this.options.mode),
       'process.static': this.isStatic
     }
-    _.each(this.options.env, (value, key) => {
+    Object.entries(this.options.env).forEach(([key, value]) => {
       env['process.env.' + key] =
-        ['boolean', 'number'].indexOf(typeof value) !== -1
+        ['boolean', 'number'].includes(typeof value)
           ? value
           : JSON.stringify(value)
     })
@@ -153,15 +153,14 @@ export default class WebpackBaseConfig {
         test: /\.jsx?$/,
         exclude: (file) => {
           // not exclude files outside node_modules
-          if (/node_modules/.test(file)) {
-            for (const module of [/\.vue\.js/].concat(this.options.build.transpile)) {
-              // item in transpile can be string or regex object
-              if (module.test(file)) {
-                return false
-              }
-            }
-            return true
+          if (!/node_modules/.test(file)) {
+            return false
           }
+
+          // item in transpile can be string or regex object
+          const modulesToTranspile = [/\.vue\.js/].concat(this.options.build.transpile)
+
+          return !modulesToTranspile.some(module => module.test(file))
         },
         use: perfLoader.pool('js', {
           loader: 'babel-loader',
diff --git a/lib/builder/webpack/plugins/vue/client.js b/lib/builder/webpack/plugins/vue/client.js
index d8fac901fe..2fe4eff5ea 100644
--- a/lib/builder/webpack/plugins/vue/client.js
+++ b/lib/builder/webpack/plugins/vue/client.js
@@ -23,7 +23,7 @@ export default class VueSSRClientPlugin {
 
       const asyncFiles = allFiles
         .filter(file => isJS(file) || isCSS(file))
-        .filter(file => initialFiles.indexOf(file) < 0)
+        .filter(file => !initialFiles.includes(file))
 
       const manifest = {
         publicPath: stats.publicPath,
diff --git a/lib/builder/webpack/server.js b/lib/builder/webpack/server.js
index 687d0327fd..f40ee52837 100644
--- a/lib/builder/webpack/server.js
+++ b/lib/builder/webpack/server.js
@@ -13,7 +13,7 @@ export default class WebpackServerConfig extends BaseConfig {
   }
 
   devtool() {
-    return 'cheap-source-map'
+    return 'cheap-module-inline-source-map'
   }
 
   env() {
diff --git a/lib/builder/webpack/utils/style-loader.js b/lib/builder/webpack/utils/style-loader.js
index b93bd91bb5..2dd328f790 100644
--- a/lib/builder/webpack/utils/style-loader.js
+++ b/lib/builder/webpack/utils/style-loader.js
@@ -1,4 +1,5 @@
 import MiniCssExtractPlugin from 'mini-css-extract-plugin'
+import { wrapArray } from '../../../common/utils'
 import PostcssConfig from './postcss'
 
 export default class StyleLoader {
@@ -19,7 +20,7 @@ export default class StyleLoader {
   }
 
   normalize(loaders) {
-    loaders = Array.isArray(loaders) ? loaders : [loaders]
+    loaders = wrapArray(loaders)
     return loaders.map(loader => (typeof loader === 'string' ? { loader } : loader))
   }
 
@@ -28,9 +29,7 @@ export default class StyleLoader {
     // style-resources-loader
     // https://github.com/yenshih/style-resources-loader
     if (extResource) {
-      const patterns = Array.isArray(extResource)
-        ? extResource
-        : [extResource]
+      const patterns = wrapArray(extResource)
 
       return {
         loader: 'style-resources-loader',
diff --git a/lib/common/options.js b/lib/common/options.js
index c27f273346..d2217528c8 100644
--- a/lib/common/options.js
+++ b/lib/common/options.js
@@ -97,18 +97,14 @@ Options.from = function (_options) {
   // Populate modulesDir
   options.modulesDir = []
     .concat(options.modulesDir)
-    .concat(path.join(options.nuxtDir, 'node_modules'))
-    .filter(hasValue)
+    .concat(path.join(options.nuxtDir, 'node_modules')).filter(hasValue)
     .map(dir => path.resolve(options.rootDir, dir))
 
-  // Sanitize extensions
-  if (options.extensions.indexOf('js') === -1) {
-    options.extensions.unshift('js')
-  }
+  const mandatoryExtensions = ['js', 'mjs']
 
-  if (options.extensions.indexOf('mjs') === -1) {
-    options.extensions.unshift('mjs')
-  }
+  options.extensions = mandatoryExtensions
+    .filter(ext => !options.extensions.includes(ext))
+    .concat(options.extensions)
 
   // If app.html is defined, set the template path to the user template
   if (options.appTemplatePath === undefined) {
diff --git a/lib/common/utils.js b/lib/common/utils.js
index 01d1849e08..730eaec9ab 100644
--- a/lib/common/utils.js
+++ b/lib/common/utils.js
@@ -14,6 +14,15 @@ export const waitFor = function waitFor(ms) {
   return new Promise(resolve => setTimeout(resolve, ms || 0))
 }
 
+export const isString = function isString(obj) {
+  return typeof obj === 'string' || obj instanceof String
+}
+export const startsWithAlias = aliasArray => str => aliasArray.some(c => str.startsWith(c))
+
+export const startsWithSrcAlias = startsWithAlias(['@', '~'])
+
+export const startsWithRootAlias = startsWithAlias(['@@', '~~'])
+
 async function promiseFinally(fn, finalFn) {
   let result
   try {
@@ -46,7 +55,7 @@ export const urlJoin = function urlJoin() {
 }
 
 export const isUrl = function isUrl(url) {
-  return url.indexOf('http') === 0 || url.indexOf('//') === 0
+  return ['http', '//'].some(str => url.startsWith(str))
 }
 
 export const promisifyRoute = function promisifyRoute(fn, ...args) {
@@ -139,11 +148,10 @@ const reqSep = /\//g
 const sysSep = _.escapeRegExp(path.sep)
 const normalize = string => string.replace(reqSep, sysSep)
 
-export const r = function r() {
-  const args = Array.prototype.slice.apply(arguments)
-  const lastArg = _.last(args)
+export const r = function r(...args) {
+  const lastArg = args[args.length - 1]
 
-  if (lastArg.indexOf('@') === 0 || lastArg.indexOf('~') === 0) {
+  if (startsWithSrcAlias(lastArg)) {
     return wp(lastArg)
   }
 
@@ -155,7 +163,7 @@ export const relativeTo = function relativeTo() {
   const dir = args.shift()
 
   // Keep webpack inline loader intact
-  if (args[0].indexOf('!') !== -1) {
+  if (args[0].includes('!')) {
     const loaders = args.shift().split('!')
 
     return loaders.concat(relativeTo(dir, loaders.pop(), ...args)).join('!')
@@ -165,7 +173,7 @@ export const relativeTo = function relativeTo() {
   const _path = r(...args)
 
   // Check if path is an alias
-  if (_path.indexOf('@') === 0 || _path.indexOf('~') === 0) {
+  if (startsWithSrcAlias(_path)) {
     return _path
   }
 
@@ -180,22 +188,22 @@ export const relativeTo = function relativeTo() {
 
 export const flatRoutes = function flatRoutes(router, _path = '', routes = []) {
   router.forEach((r) => {
-    if (!r.path.includes(':') && !r.path.includes('*')) {
-      /* istanbul ignore if */
-      if (r.children) {
-        if (_path === '' && r.path === '/') {
-          routes.push('/')
-        }
-        flatRoutes(r.children, _path + r.path + '/', routes)
-      } else {
-        _path = _path.replace(/^\/+$/, '/')
-        routes.push(
-          (r.path === '' && _path[_path.length - 1] === '/'
-            ? _path.slice(0, -1)
-            : _path) + r.path
-        )
-      }
+    if ([':', '*'].some(c => r.path.includes(c))) {
+      return
     }
+    /* istanbul ignore if */
+    if (r.children) {
+      if (_path === '' && r.path === '/') {
+        routes.push('/')
+      }
+      return flatRoutes(r.children, _path + r.path + '/', routes)
+    }
+    _path = _path.replace(/^\/+$/, '/')
+    routes.push(
+      (r.path === '' && _path[_path.length - 1] === '/'
+        ? _path.slice(0, -1)
+        : _path) + r.path
+    )
   })
   return routes
 }
@@ -214,7 +222,7 @@ function cleanChildrenRoutes(routes, isChild = false) {
   })
   routes.forEach((route) => {
     route.path = isChild ? route.path.replace('/', '') : route.path
-    if (route.path.indexOf('?') > -1) {
+    if (route.path.includes('?')) {
       const names = route.name.split('-')
       const paths = route.path.split('/')
       if (!isChild) {
@@ -259,15 +267,15 @@ export const createRoutes = function createRoutes(files, srcDir, pagesDir) {
     let parent = routes
     keys.forEach((key, i) => {
       // remove underscore only, if its the prefix
-      const sanitizedKey = key.indexOf('_') === 0
-        ? key.replace('_', '')
-        : key
+      const sanitizedKey = key.startsWith('_') ? key.substr(1) : key
+
       route.name = route.name
         ? route.name + '-' + sanitizedKey
         : sanitizedKey
       route.name += key === '_' ? 'all' : ''
       route.chunkName = file.replace(/\.(vue|js)$/, '')
-      const child = _.find(parent, { name: route.name })
+      const child = parent.find(parentRoute => parentRoute.name === route.name)
+
       if (child) {
         child.children = child.children || []
         parent = child.children
@@ -275,13 +283,9 @@ export const createRoutes = function createRoutes(files, srcDir, pagesDir) {
       } else if (key === 'index' && i + 1 === keys.length) {
         route.path += i > 0 ? '' : '/'
       } else {
-        route.path += '/' +
-            (key === '_'
-              ? '*'
-              : key.indexOf('_') === 0
-                ? key.replace('_', ':')
-                : key)
-        if (key !== '_' && key.indexOf('_') === 0) {
+        route.path += '/' + getRoutePathExtension(key)
+
+        if (key.startsWith('_') && key.length > 1) {
           route.path += '?'
         }
       }
@@ -298,12 +302,13 @@ export const createRoutes = function createRoutes(files, srcDir, pagesDir) {
       // Order: /static, /index, /:dynamic
       // Match exact route before index: /login before /index/_slug
       if (a.path === '/') {
-        return /^\/(:|\*)/.test(b.path) ? -1 : 1
+        return DYNAMIC_ROUTE_REGEX.test(b.path) ? -1 : 1
       }
       if (b.path === '/') {
-        return /^\/(:|\*)/.test(a.path) ? 1 : -1
+        return DYNAMIC_ROUTE_REGEX.test(a.path) ? 1 : -1
       }
-      let i = 0
+
+      let i
       let res = 0
       let y = 0
       let z = 0
@@ -313,8 +318,8 @@ export const createRoutes = function createRoutes(files, srcDir, pagesDir) {
         if (res !== 0) {
           break
         }
-        y = _a[i] === '*' ? 2 : _a[i].indexOf(':') > -1 ? 1 : 0
-        z = _b[i] === '*' ? 2 : _b[i].indexOf(':') > -1 ? 1 : 0
+        y = _a[i] === '*' ? 2 : _a[i].includes(':') ? 1 : 0
+        z = _b[i] === '*' ? 2 : _b[i].includes(':') ? 1 : 0
         res = y - z
         // If a.length >= b.length
         if (i === _b.length - 1 && res === 0) {
@@ -361,3 +366,25 @@ export const determineGlobals = function determineGlobals(globalName, globals) {
   }
   return _globals
 }
+
+const getRoutePathExtension = (key) => {
+  if (key === '_') {
+    return '*'
+  }
+
+  if (key.startsWith('_')) {
+    return `:${key.substr(1)}`
+  }
+
+  return key
+}
+
+const DYNAMIC_ROUTE_REGEX = /^\/(:|\*)/
+
+/**
+ * Wraps value in array if it is not already an array
+ *
+ * @param  {any} value
+ * @return {array}
+ */
+export const wrapArray = value => Array.isArray(value) ? value : [value]
diff --git a/lib/core/nuxt.js b/lib/core/nuxt.js
index 0cc4a330e3..d9b259e085 100644
--- a/lib/core/nuxt.js
+++ b/lib/core/nuxt.js
@@ -11,7 +11,7 @@ import esm from 'esm'
 import ip from 'ip'
 
 import Options from '../common/options'
-import { sequence } from '../common/utils'
+import { sequence, startsWithRootAlias, startsWithSrcAlias } from '../common/utils'
 import packageJSON from '../../package.json'
 
 import ModuleContainer from './module'
@@ -254,11 +254,11 @@ export default class Nuxt {
       return modulePath
     }
 
-    if (path.indexOf('@@') === 0 || path.indexOf('~~') === 0) {
+    if (startsWithRootAlias(path)) {
       return join(this.options.rootDir, path.substr(2))
     }
 
-    if (path.indexOf('@') === 0 || path.indexOf('~') === 0) {
+    if (startsWithSrcAlias(path)) {
       return join(this.options.srcDir, path.substr(1))
     }