Javascript - "arguments.callee" technique : this value points to the anonymous function in which the code is executing.

gistfile1.txt

var todo = items.concat(); //create a clone of the original array
 
setTimeout(function(){
  //get next item in the array and process it
  process(todo.shift());
 
  //if there's more items to process, create another timer
  if(todo.length > 0){
    setTimeout(arguments.callee, 25); // arguments.callee = anonymous function where the code is executing
  } else {
    callback(items);
  }
}, 25);