break array of objects into separate arrays based on a property

This is an easy job for Array.reduce(...):

function groupBy(arr, property) {  return arr.reduce(function(memo, x) {    if (!memo[x[property]]) { memo[x[property]] = []; }    memo[x[property]].push(x);    return memo;  }, {});}var o = groupBy(arr, 'type'); // => {orange:[...], banana:[...]}o.orange; // => [{"type":"orange","title":"First"},{"type":"orange","title":"Second"}]o.banana; // => [{"type":"banana","title":"Third"},{"type":"banana","title":"Fourth"}]

Of course, if your target browser(s) do not support ECMAScript 262 5th edition then you'll have to implement "reduce" by yourself, or use a polyfill library, or choose another answer.

[Update] Here's a solution that should work with any version of JavaScript:

function groupBy2(xs, prop) {  var grouped = {};  for (var i=0; i<xs.length; i++) {    var p = xs[i][prop];    if (!grouped[p]) { grouped[p] = []; }    grouped[p].push(xs[i]);  }  return grouped;}

JQuery and Underscore are both options to use.

Underscore's groupBy does exactly what you need.

_.groupBy(arr, "type")

This assumes an array of objects:

function groupBy(array, property) {    var hash = {};    for (var i = 0; i < array.length; i++) {        if (!hash[array[i][property]]) hash[array[i][property]] = [];        hash[array[i][property]].push(array[i]);    }    return hash;}groupBy(arr,'type')  // Object {orange: Array[2], banana: Array[2]}groupBy(arr,'title') // Object {First: Array[1], Second: Array[1], Third: Array[1], Fourth: Array[1]}