Suppose you have an array of object:

var array = [   {a:13, b:false },
        {a:7, b:true },
        {a:78, b:true } ]       

The old, ECMAScript 3 way of checking for objects, in which b is true would be a simple for-loop:

var results = [];
for (var i=0; i
Ok, that's working, but not very elegant nor concise. Luckily, ECMAScript 5 offers a nicer way:
var results = array.filter( function(item) {
    return item.b;      // if item.b is true
});