jerryscript/tools/babel/README.md
Daniella Barsony e5702edab4
Update Babel ReadMe (#3673)
Remove Array.prototype.fill and Array.from from missing features that requires polyfill

JerryScript-DCO-1.0-Signed-off-by: Daniella Barsony bella@inf.u-szeged.hu
2020-04-15 16:53:14 +02:00

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# 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](https://babeljs.io/).
## Example
```javascript
//Before
const fn = () => 1;
//After conversion
var fn = function fn() {
return 1;
};
```
## Table of Contents
* **[Getting ready](#getting-ready)**
* Installing node.js and npm
* **[Using babel](#using-babel)**
* **[Missing features/Polyfill](#missing-features)**
## Getting ready [](#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
```bash
$ nodejs --version
Output: v8.10.0
```
Next up is installing **npm** with the following command
`$ sudo apt install npm`
Verify installation by typing:
```bash
$ npm --version
Output: 6.10.2
```
### 2. Using babel [](#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.