splice.js

/**
 * @author Robbert Broersma <http://robbertbroersma.nl/>
 * @license © 2013, The Knights Who Say NIH B.V. All rights reserved.
 */

var List = {};

/**
 * Works like arr.splice(), but without constructing an array
 * with the removed values to reduce garbage collection.
 * 
 * Same combination as Node.removeChild() vs Node.remove().
 * 
 * @param  {Array} arr
 * @param  {number} start
 * @param  {number} howMany
 */
List.removeSlice = function (arr, start, howMany)
{
    var before,
        after,
        newIndex,
        newLength,
        oldIndex,
        end,
        l = arr.length;

    if (start < 0)
        start += l;

    end = start + howMany;

    if (start < end)
    {
        if (start <= 0 && end >= l)
        {
            while (l--)
                arr.pop();
        }
        else if (start === 0)
        {
            while (end--)
                arr.shift();
        }
        else if (end === l)
        {
            end -= start;

            while (end--)
                arr.pop();
        }
        else
        {
            before = start;
            after = l - start - howMany

            if (after > before)
            {
                while (end --> start)
                {
                    arr[start] = arr[0];
                    arr.shift();
                }
            }
            else
            {
                oldIndex = start + howMany;
                newIndex = start;
                newLength = l - howMany;

                while (newIndex < newLength)
                {
                    arr[newIndex] = arr[oldIndex];
                    oldIndex++;
                    newIndex++;
                }

                while (howMany--)
                    arr.pop();
            }
        }
    }
};