Removes 136,000 positions from an array of 278,000 in 50ms.

gistfile1.txt

function filterOutPositions(array, positions) // utility code, @param -- positions to remove
  {
    var BE_DELETED = {};

    var arr = array.slice(0); // Clone the array so it can be re-used (non-destructive)
    var pos_len = positions.length;
    for (var i=0; i < pos_len; i++)
    {
      arr[ positions[i] ] = BE_DELETED;
    }

    return arr.filter(function(arr_item) { return arr_item !== BE_DELETED; });
  }