Add ecmaScript option

Author: l1bbcsg

README.md

@@ -28,6 +28,7 @@ module.exports = (config) => {
 		moduleResolverPreprocessor: {
 			addExtension: 'js',
 			customResolver: null,
+			ecmaVersion: 6,
 			aliases: {
 				project: "./project"
 			}
@@ -97,3 +98,9 @@ import Foo from 'foo';
 // Rewrites to
 import Foo from 'http://example.com/foo';
 ```
+
+#### `ecmaVersion`
+
+Default value: `6`
+
+ECMAScript version as accepted by [espree](https://github.com/eslint/espree), e.g. `6`, `9`, `2015`, `2018`.

index.js

@@ -4,6 +4,7 @@ const path = require('path');
 const defaultOptions = {
 	addExtension: 'js',
 	customResolver: null,
+	ecmaVersion: 6,
 	aliases: {}
 };
 
@@ -68,6 +69,7 @@ const createModuleResolverPreprocessor = (karmaConfig, args = {}, config = {}, l
 		let ast = null;
 		try {
 			ast = espree.parse(content, {
+				ecmaVersion: options.ecmaVersion,
 				sourceType: 'module'
 			});
 		} catch (e) {