range-js

This library provides a ES6 - ready lazy ranges.
Until ES6 is implemented, it is transpiled down to ES5.

Installation

npm install range-js

Usage

Node.js

var Range = require('range-js').Range;

Vanilla Browser JS

Browser builds are found in dist/browser/index.js.
The Range constructor is exposed as window.IterateableRange.

Babelify (Browserify + Babel)

If you are using Babelify you can import the module in ES6 - Style.

import { Range } from 'range-js';

Basic Usage

var range = new Range(1, 10); // => Range { start: 1, end: 10, step: 1 }

console.log(range.count()) // => 10
console.log(range.toArray()); // => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Range objects expose @@iterator so you can use for ... of to iterate.

var alphabet = new Range('a', 'z');

for (let letter of alphabet) {
    console.log(letter);
}

... but generally you'll be using the forEach method.

var alphabet = new Range('a', 'z');

alphabet.forEach(function(letter, i){
    console.assert(letter === i); // Consistent to Array.prototype.forEach
    console.log(letter);
});

Step

You can specify a step number for the range.

let range = new Range(1, 100, 5);

console.log(range.toArray()); // => [1, 6, 11, 16, 21, 26, 31, 36, 41, 46, 51, 56, 61, 66, 71, 76, 81, 86, 91, 96]
console.log(range.count()); // => 20

Infinity + Limit

The end of the range may be Infinity but only in combination with the limit (4th) parameter equal to a positive integer.

let range = new Range(0, Infinity, 10000, 10);

console.log(range.toArray()); // => [0, 10000, 20000, 30000, 40000, 50000, 60000, 70000, 80000, 90000]
console.log(range.count()); // => 10