refactor: remove usage of var in babel-preset-react-app

Author: tobiasbueschel

packages/babel-preset-react-app/README.md

@@ -56,7 +56,7 @@ Make sure you have a `tsconfig.json` file at the root directory. You can also us
 
 Absolute paths are enabled by default for imports. To use relative paths instead, set the `absoluteRuntime` option in `.babelrc` to `false`:
 
-```
+```json
 {
   "presets": [["react-app", { "absoluteRuntime": false }]]
 }

packages/babel-preset-react-app/create.js

@@ -25,36 +25,36 @@ module.exports = function (api, opts, env) {
     opts = {};
   }
 
-  var isEnvDevelopment = env === 'development';
-  var isEnvProduction = env === 'production';
-  var isEnvTest = env === 'test';
+  const isEnvDevelopment = env === 'development';
+  const isEnvProduction = env === 'production';
+  const isEnvTest = env === 'test';
 
-  var useESModules = validateBoolOption(
+  const useESModules = validateBoolOption(
     'useESModules',
     opts.useESModules,
     isEnvDevelopment || isEnvProduction
   );
-  var isFlowEnabled = validateBoolOption('flow', opts.flow, true);
-  var isTypeScriptEnabled = validateBoolOption(
+  const isFlowEnabled = validateBoolOption('flow', opts.flow, true);
+  const isTypeScriptEnabled = validateBoolOption(
     'typescript',
     opts.typescript,
     true
   );
-  var areHelpersEnabled = validateBoolOption('helpers', opts.helpers, true);
-  var useAbsoluteRuntime = validateBoolOption(
+  const areHelpersEnabled = validateBoolOption('helpers', opts.helpers, true);
+  const useAbsoluteRuntime = validateBoolOption(
     'absoluteRuntime',
     opts.absoluteRuntime,
     true
   );
 
-  var absoluteRuntimePath = undefined;
+  let absoluteRuntimePath = undefined;
   if (useAbsoluteRuntime) {
     absoluteRuntimePath = path.dirname(
       require.resolve('@babel/runtime/package.json')
     );
   }
 
-  var hasJsxRuntime = Boolean(
+  const hasJsxRuntime = Boolean(
     api.caller(caller => !!caller && caller.hasJsxRuntime)
   );
 

packages/babel-preset-react-app/dependencies.js

@@ -31,19 +31,19 @@ module.exports = function (api, opts) {
   // https://github.com/babel/babel/issues/4539
   // https://github.com/facebook/create-react-app/issues/720
   // It’s also nice that we can enforce `NODE_ENV` being specified.
-  var env = process.env.BABEL_ENV || process.env.NODE_ENV;
-  var isEnvDevelopment = env === 'development';
-  var isEnvProduction = env === 'production';
-  var isEnvTest = env === 'test';
+  const env = process.env.BABEL_ENV || process.env.NODE_ENV;
+  const isEnvDevelopment = env === 'development';
+  const isEnvProduction = env === 'production';
+  const isEnvTest = env === 'test';
 
-  var areHelpersEnabled = validateBoolOption('helpers', opts.helpers, false);
-  var useAbsoluteRuntime = validateBoolOption(
+  const areHelpersEnabled = validateBoolOption('helpers', opts.helpers, false);
+  const useAbsoluteRuntime = validateBoolOption(
     'absoluteRuntime',
     opts.absoluteRuntime,
     true
   );
 
-  var absoluteRuntimePath = undefined;
+  let absoluteRuntimePath = undefined;
   if (useAbsoluteRuntime) {
     absoluteRuntimePath = path.dirname(
       require.resolve('@babel/runtime/package.json')