数组切割

将一个大的数组按照长度来划分成不同的小数组

    var chunk = function (array, size) {
        var result = [];
        for (var x = 0; x < Math.ceil(array.length / size); x++) {
            var start = x * size;
            var end = start + size;
            result.push(array.slice(start, end));
        }
        return result;
    }