Switching to using terser instead of uglify-es (so it's maintained). …

…see #721

js/grunt/generateCoverage.js

@@ -6,7 +6,7 @@
  *
  * To generate coverage for a sim (or other codebase):
  * 1. Build with instrumentation added (preferably without minification):
- *    $ grunt --uglify=false --instrument=true
+ *    $ grunt --minify.uglify=false --instrument=true
  * 2. Run the instrumented version from the build directory.
  * 3. When done, in the JS console, `copy( __coverage__ )` to copy JSON coverage information into your clipboard.
  * 4. Paste it into build/instrumentation/coverage.json

js/grunt/minify.js

@@ -11,7 +11,7 @@
 // modules
 const _ = require( 'lodash' ); // eslint-disable-line require-statement-match
 const transpile = require( './transpile' );
-const uglifyES = require( 'uglify-es' ); // eslint-disable-line require-statement-match
+const terser = require( 'terser' );
 
 const MINIFY_DEFAULTS = {
   minify: true,
@@ -75,8 +75,7 @@ const minify = function( js, options ) {
   }
 
   if ( uglify ) {
-
-    const result = uglifyES.minify( js, uglifyOptions );
+    const result = terser.minify( js, uglifyOptions );
 
     if ( result.error ) {
       console.log( result.error );

package.json

@@ -28,7 +28,7 @@
     "request": "^2.87.0",
     "request-promise-native": "^1.0.7",
     "requirejs": "~2.3.5",
-    "uglify-es": "~3.1.10",
+    "terser": "~4.6.4",
     "url-loader": "^3.0.0",
     "webpack": "^4.41.4",
     "webpack-cli": "^3.3.10",