remove single item from array in javascript

pull.js

/* Removes first specified item from array, if it exists
   Use like: ["55","35"].pull("35")
   Handles cases where "35" isn't in the array
   Modifies array and returns pulled item
*/
Array.prototype.pull = function(x) {
  var index = this.indexOf(x);
  var to_return = undefined;
  if(index !== -1) {
    this.splice(index, 1);
    to_return = x;
  }
  return to_return;
}