gistfile1.js

var array = ['a', 'b', 'c', 'd', 'e', 'f', 'g'];
var size = 2;

var result = chunk(array, size);
// console.log(result); // [['a', 'b'], ['c', 'd'], ['e', 'f'], ['g']]

function chunk(array, size) {
    var len = array.length;
    var index = 0;
    var result = [];

    if (len < 1 || len < size) {
        return array;
    }

    do {
        result.push(array.slice(index, index + size));
        index = index + size;
    } while (index < len);

    return result;
}