Issue 3505 | Transpile to ES5

gulpfile.js

@@ -410,6 +410,10 @@ function bundleTask(opts) {
       .pipe(gulpif(opts.isBuild, uglify({
         mangle: { reserved: [ 'MetamaskInpageProvider' ] },
       })))
+      // Transpile to ES5
+      .pipe(gulpif(opts.isBuild, babel({
+        presets: ['env']
+      })))
       // writes .map file
       .pipe(gulpif(debug, sourcemaps.write('./')))
       // write completed bundles

package.json

@@ -10,9 +10,10 @@
     "mock": "beefy development/mock-dev.js:bundle.js --live --open --index=./development/index.html --cwd ./",
     "watch": "mocha watch --recursive \"test/unit/**/*.js\"",
     "mascara": "gulp build && cross-env METAMASK_DEBUG=true node ./mascara/example/server",
-    "dist": "npm run dist:clear && npm install && gulp dist",
+    "dist": "npm run dist:clear && npm install && gulp dist && npm run test:es5",
     "dist:clear": "rm -rf node_modules/eth-contract-metadata && rm -rf node_modules/eth-phishing-detect",
     "test": "npm run lint && npm run test:coverage && npm run test:integration",
+    "test:es5": "es-check es5 ./dist/**/*.js",
     "test:unit": "cross-env METAMASK_ENV=test mocha --exit --require babel-core/register --require test/helper.js --recursive \"test/unit/**/*.js\"",
     "test:single": "cross-env METAMASK_ENV=test mocha --require test/helper.js",
     "test:integration": "npm run test:integration:build && npm run test:flat && npm run test:mascara",
@@ -200,6 +201,7 @@
     "envify": "^4.0.0",
     "enzyme": "^3.3.0",
     "enzyme-adapter-react-15": "^1.0.5",
+    "es-check": "^2.0.2",
     "eslint-plugin-chai": "0.0.1",
     "eslint-plugin-mocha": "^4.9.0",
     "eslint-plugin-react": "^7.4.0",