Update JavaScript Minify operation to support ES6.

src/core/operations/JavaScriptMinify.mjs

@@ -4,10 +4,9 @@
  * @license Apache-2.0
  */
 
+import OperationError from "../errors/OperationError.mjs";
 import Operation from "../Operation.mjs";
-import * as esprima from "esprima";
-import escodegen from "escodegen";
-import esmangle from "esmangle";
+import Terser from "terser";
 
 /**
  * JavaScript Minify operation
@@ -34,22 +33,11 @@ class JavaScriptMinify extends Operation {
      * @returns {string}
      */
     run(input, args) {
-        let result = "";
-        const AST = esprima.parseScript(input),
-            optimisedAST = esmangle.optimize(AST, null),
-            mangledAST = esmangle.mangle(optimisedAST);
-
-        result = escodegen.generate(mangledAST, {
-            format: {
-                renumber:    true,
-                hexadecimal: true,
-                escapeless:  true,
-                compact:     true,
-                semicolons:  false,
-                parentheses: false
-            }
-        });
-        return result;
+        const result = Terser.minify(input);
+        if (result.error) {
+            throw new OperationError(`Error minifying JavaScript. (${result.error})`);
+        }
+        return result.code;
     }
 
 }