Avoid func declarations using function keyword (#2813)

We had only a few function expressions declared with the function keyword; almost everything is using function declarations.

This came up after this discussion: https://github.com/badges/shields/pull/2803#discussion_r249011621 though is actually not related ot that example.

What’s being removed is a third option, which is assigning to a variable a function expression using the `function` keyword. There’s still room for the programmer to choose between arrow function expressions and function declarations.

.eslintrc.yml

@@ -38,6 +38,7 @@ rules:
   object-shorthand: ['error', 'properties']
   prefer-template: 'error'
   promise/prefer-await-to-then: 'error'
+  func-style: ['error', 'declaration', { 'allowArrowFunctions': true }]
 
   # Mocha-related.
   mocha/no-exclusive-tests: 'error'

lib/error-helper.js

@@ -9,7 +9,7 @@ const defaultErrorMessages = {
   404: 'not found',
 }
 
-const checkErrorResponse = function(badgeData, err, res, errorMessages = {}) {
+function checkErrorResponse(badgeData, err, res, errorMessages = {}) {
   errorMessages = { ...defaultErrorMessages, ...errorMessages }
   if (err != null) {
     badgeData.text[1] = 'inaccessible'

services/docker/docker-helpers.js

@@ -2,14 +2,14 @@
 
 const dockerBlue = '066da5' // see https://github.com/badges/shields/pull/1690
 
-const buildDockerUrl = function(badgeName) {
+function buildDockerUrl(badgeName) {
   return {
     base: `docker/${badgeName}`,
     pattern: ':user/:repo',
   }
 }
 
-const getDockerHubUser = function(user) {
+function getDockerHubUser(user) {
   return user === '_' ? 'library' : user
 }
 

services/packagist/packagist-license.service.js

@@ -59,15 +59,13 @@ module.exports = class PackagistLicense extends LegacyService {
             // Note: if you change the latest version detection algorithm here,
             // change it above (for the actual version badge).
             let version
-            const unstable = function(ver) {
-              return /dev/.test(ver)
-            }
+            const isUnstable = ({ version }) => version.includes('dev')
             // Grab the latest stable version, or an unstable
             for (const versionName in data.package.versions) {
               const current = data.package.versions[versionName]
 
               if (version !== undefined) {
-                if (unstable(version.version) && !unstable(current.version)) {
+                if (isUnstable(version) && !isUnstable(current)) {
                   version = current
                 } else if (
                   version.version_normalized < current.version_normalized

services/pypi/pypi-helpers.js

@@ -8,7 +8,7 @@
   our own functions to parse and sort django versions
 */
 
-const parseDjangoVersionString = function(str) {
+function parseDjangoVersionString(str) {
   if (typeof str !== 'string') {
     return false
   }
@@ -21,8 +21,8 @@ const parseDjangoVersionString = function(str) {
   }
 }
 
-// sort an array of django versions low to high
-const sortDjangoVersions = function(versions) {
+// Sort an array of django versions low to high.
+function sortDjangoVersions(versions) {
   return versions.sort((a, b) => {
     if (
       parseDjangoVersionString(a).major === parseDjangoVersionString(b).major
@@ -38,8 +38,8 @@ const sortDjangoVersions = function(versions) {
   })
 }
 
-// extract classifiers from a pypi json response based on a regex
-const parseClassifiers = function(parsedData, pattern) {
+// Extract classifiers from a pypi json response based on a regex.
+function parseClassifiers(parsedData, pattern) {
   const results = []
   for (let i = 0; i < parsedData.info.classifiers.length; i++) {
     const matched = pattern.exec(parsedData.info.classifiers[i])

services/response-fixtures.js

@@ -1,9 +1,9 @@
 'use strict'
 
-const invalidJSON = function() {
-  return [200, '{{{{{invalid json}}', { 'Content-Type': 'application/json' }]
-}
-
 module.exports = {
-  invalidJSON,
+  invalidJSON: () => [
+    200,
+    '{{{{{invalid json}}',
+    { 'Content-Type': 'application/json' },
+  ],
 }