babel.md

Babel is a transpiler (translator + compiler) and it converts modern code into old code, able to run in older browsers.

npm install babel-cli babel-core babel-preset-env

babel-cli - Command line interface. Takes a js file and returns a transpiled one. babel-core - The transpiling logic.
babel-preset-env - Each new javascript feature has a separate plugin. Intead of installing them one by one, we can install a preset containing all of them.

To run the transpiler we can use:

# Use the env preset to transpile index.js and put the output in the build folder in index.js.
babel --presets env index.js -o build/index.js

This command is for one file. In order to transpile many files, a bundler like Webpack is needed. Here, every file is transpiler first, before being added to the bundle.

We can add this in package.json for convenience:

{
    "scripts": {
        "babel": "babel --presets env index.js -o build/index.js"
    }
}