jerryscript/tools/babel

Converting incompatible features with Babel

To run ES6 sources with JerryScript that use unsupported language features, you can use Babel to transpile your code, which will output a semantically equivalent source file, where the unsupported features are replaced with ES5.1 code. Babel is a JavaScript compiler that is used to convert ES2015+ code into a backward-compatible version. You can find more information here.

Example

//Before
const fn = () => 1;

//After conversion

var fn = function fn() {
  return 1;
};

Table of Contents

• Getting ready
  • Installing node.js and npm
• Using babel
• Missing features/Polyfill

Getting ready

1. Node.js and npm

Start by updating the packages with

$ sudo apt update

Install nodejs using the apt package manager

$ sudo apt install nodejs

Check the version of node.js to verify that it installed

$ nodejs --version
Output: v8.10.0

Next up is installing npm with the following command

$ sudo apt install npm

Verify installation by typing:

$ npm --version
Output: 6.10.2

2. Using babel

Assuming you're in the tools/babel folder,

$ sudo npm install

After installing the dependencies it is ready to use.

Place the files/directories you want transpiled to the babel folder and run

$ npm run transpile [name of input file/directory] [(OPTIONAL)name of output file/directory]

If you want to use the same name, then only give the name once.

Missing features/Polyfill

Some features aren't implemented yet and found no babel plug-in for them.

• Array.from
• Array.prototype.fill
• String.prototype.codePointAt

In the case you encounter those, use the polyfill found on the linked sites. Also, be aware there could be more.