Validate JS source code against ES5 and report possible syntax errors before shipping to production to make your code safe on iOS 9, iOS 10 or other ES6+ incompatible platforms (IE11).

The earlier you find ES5 incompatibility errors, the earlier you can fix them.

npx es5-validator FILE_TO_VALIDATE1.js [FILE_TO_VALIDATE2.js] [https://some-cdn/es.min.js]

npm i es5-validator --save-dev

package.json

{
  "scripts": {
    "lint:es5": "es5-validator es6.js"
  }
}

es6.js

function func(foo = '') {}
const bar = 1;

npm run lint:es5

Result:

[es5-validator] Your code is not ES5 Compatible. It's not ready to ship to production, otherwise it will break you App on iOS 9 or iOS 10.

Error: ECMAScript 5 validate failed when parsing es6.js.formatted (1, 18)


> 1 | function func(foo = '') {}
    |                  ^ Invalid ECMAScript 5 syntax
  2 | const bar = 1;

Demo repo.

To avoid breaking you App by shipping ES6+ code to production silently.

Detect syntax error by parsing source code aganest ES5 using acorn. For more details, you can read the code.

When encountering a syntax error, the parser will raise a SyntaxError object with a meaningful message. The error object will have a pos property that indicates the string offset at which the error occurred, and a loc object that contains a {line, column} object referring to that same position.

• https://www.npmjs.com/package/acorn

acorn.parse(source, {
  ecmaVersion: 5,
});

💡 Notice: Only the syntax can be detected. Methods introduced by ES6+ wont be reported. For example Object.assign will not be reported but spread operator will.

• Validate local JS file.
• Validate remote JS file. For example: npx es5-validator https://cdn.jsdelivr.net/npm/js-pinyin/index.js.
• Validate multiple JS files concurrently. For example: npx es5-validator es6-1.js es6-2.js.
• Validate inline source code directly. For example: npx es5-validator --inline "const bar = 1;".

• Validate remote js. npx es5-validator https://cdn.jsdelivr.net/npm/js-pinyin/index.js.

Give a star ❤️ if it helped you https://github.com/legend80s/es5-validator.