insert, remove, or replace array elements
array.splice(start, deleteCount, value, ...)
The array element at which the insertion and/or deletion is to begin.
deleteCount The number of elements, starting with and including start, to be deleted from array. Specify 0 to insert elements without deleting any.
value, ... Zero or more values to be inserted into array, beginning at the index specified by start.
An array containing the elements, if any, deleted from array.
splice() deletes zero or more array elements starting with and including the element start and replaces them with zero or more values specified in the argument list. Array elements that appear after the insertion or deletion are moved as necessary so that they remain contiguous with the rest of the array. Note that, unlike the similarly named slice(), splice() modifies array directly.
The operation of splice() is most easily understood through an example:
var a = [1,2,3,4,5,6,7,8] a.splice(1,2); // Returns [2,3]; a is [1,4] a.splice(1,1); // Returns ; a is  a.splice(1,0,2,3); // Returns ; a is [1 2 3]