Babel is a JavaScript compiler.
It converts modern syntax into code that older browsers understand.
In 2015 this made it possible to use ES6 features in production while IE‑only engines were still common.

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Why Babel matters

• Early access – arrow functions, classes, modules, and more without waiting for native support
• Config file – .babelrc keeps presets and plugins in one place
• Plugin system – choose only the transforms you need
• Multiple outputs – turn ES modules into CommonJS, AMD, or System formats

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Project setup

# Install CLI and the ES2015 preset locally
npm install --save-dev babel-cli babel-core babel-preset-es2015

# Optional: watcher for automatic rebuilds
npm install --save-dev babel-watch

Create .babelrc:

{
  "presets": ["es2015"]
}

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Example: Transpile a small module

src/math.js

export const PI = 3.14;
export const double = n => n * 2;

Build the file:

# One‑off build
npx babel src --out-dir lib

# Continuous build during development
npx babel-watch src --out-dir lib

lib/math.js (output)

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});
var PI = exports.PI = 3.14;
var double = exports.double = function double(n) {
  return n * 2;
};

The ES6 export statements become CommonJS assignments, ready for Node or older browsers after bundling.

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Common build integrations

• Browserify – add babelify as a transform
• Grunt / Gulp – run grunt-babel or gulp-babel in the task pipeline

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Key ES6 features you can ship today

• let and const block‑scoped variables
• Arrow functions with lexical this
• Classes with concise method syntax
• Template literals with ${} interpolation
• Destructuring for arrays and objects

Each transform is handled by the preset, so the workflow stays simple after the initial install.

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Babel removes the waiting game.
Write modern JavaScript, compile once, and run everywhere.