babel-plugin-loop-optimizer

Optimizes .forEach and .map statements to for stements

Installation

$ npm install babel-plugin-loop-optimizer

Usage

Via .babelrc (Recommended)

.babelrc

{
  "plugins": ["babel-plugin-loop-optimizer"]
}

Via CLI

$ babel --plugins loop-optimizer script.js

Via Node API

require('babel').transform('code', {
  plugins: ['loop-optimizer']
});

Bugs?

Now you may say "wait, wait, wait!" This optimizes on things that aren't just arrays! My map#forEach is optimized too! To fix this, add a comment that says // O: KEEP right before the line on which you use the forEach. Examples:

var m = new Map();
// O: KEEP
m.forEach(f)

or:

var s = new Set();
// O: KEEP
for (var i = 0; i < 5; s.forEach(f)) {
    // ...
}

This is required since it is not possible to determine an object's type at compile-time.

Example

function timesTwo(arr) {
	return arr.map(n => n * 2);
}

to:

function timesTwo(arr) {
    var _a = arr;
    var _f = n => n * 2;
    var _r = [];

    for (var _i = 0; _i < _a.length; _i++)
        _r.push(_f(_a[_i], _i, _a));

    return _r;
}

If you need any other help, don't hesitate to leave an issue