README

array.stride

Implement stride method for javascript arrays to iterate multiple elements per loop.

Installation

npm install array.stride

Usage

In node.js simply require this module. Unlike most node modules, array.stride doesn't export anything. Instead it modifies the Array prototype to implement a new method: .stride().

require('array.stride');

In the browser simply include it. There are no node.js specific code used in the module. Either copy/paste the code into your own source or inclde it in a script tag:

<script src="array.stride.js"></script>

Syntax

arr.stride( callback [, default_value ] )

Parameters

callback : Function to execute for each iteration through the array, takes one or more arguments.
default_value : Optional argument to specify what the value of an argument should be if there are not enough elements in the array. If not specified the value defaults to undefined.

Description

Array.prototype.stride() works like Array.prototype.forEach(). It iterates through the array passing elements to a callback function. Only, instead of passing one element per iteration, stride() passes as many elements as there are function arguments.

If there are not enough elements in the array for the last iteration of the loop the remaining arguments to the callback will be undefined. Optionally you can pass a value as a second argument to .stride() for the remaining arguments.

Inside the callback function, this is set to the iteration number/count. This behavior may be overridden by calling .bind() on the callback.

Array.prototype.stride() returns an array of results of applying the callback on each element. So I lied a bit: it doesn't work like .forEach(), instead it works more like Array.prototype.map().

Examples

Example: Iterating through an array two elements at a time

The following code iterates through the array two elements at a time:

[1,2,3,4,5,6,7,8].stride(function (a,b) {
    console.log("(" + a + "|" + b + ")");
});

// logs:
(1|2)
(3|4)
(5|6)
(7|8)

Example: Iterating through an array three elements at a time

The following code generates a 3x3 2-dimensional array:

var x = [1,2,3,4,5,6,7,8].stride(function (a,b,c) {
    return [a,b,c];
});

// x is now:
[[1,2,3],
 [4,5,6],
 [7,8,undefined]]

Example: Default value

Here's how you can specify an alternate value for the undefined:

var x = [1,2,3,4,5,6,7,8].stride(function (a,b,c) {
    return [a,b,c];
},0); // <-- default_value

// x is now:
[[1,2,3],
 [4,5,6],
 [7,8,0]]

Example: this

You can use this to get the loop count:

[1,2,3,4,5,6].stride(function (a,b) {
    console.log(this + " : " + a + "|" + b);
});

// logs:
0 : 1|2
1 : 3|4
2 : 5|6

Usage no npm install needed!