babel-plugin-loop-optimizer

WARNING: This package is unmaintained. It probably still works but I am not able to maintain it. If anyone wishes to pick this up leave an issue and I can give access.

Also, that package aren't working with newest Babel (that have @babel namespace) right now.

Optimizes .forEach, .every, .find, .map, .filter 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 some optimized function. Examples:

var m = new Map();
// loop-optimizer: KEEP
m.forEach(f)

or:

var s = new Set();
// loop-optimizer: 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.

Also, if you don't want reverse order, you can disable this (optimization) behavior by adding comment // loop-optimizer: FORWARD right before the line on which you use some optimized function. Example:

let ar = [1, 2, 3]
// loop-optimizer: FORWARD
ar.forEach(console.log)

Example

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

to:

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

    for (let _i = _a.length; _i--;)
        _r.push(_f(_a[_i], _i, _a));

    return _r;
}

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