How to unshift or add to the beginning of arguments object in JavaScript

Question

I've just learned the convention for popping off the first element of the arguments array (which I also learned is actually an Object). Now I need to do the opposite. I need to use an unshift operation to add a value to the beginning of the arguments array (or Object acting like an array). Is this possible? I tried:

Array.prototype.unshift.apply('hello', arguments);

That had no effect on arguments whatsoever.

Solution

1. use .call() instead of .apply() to invoke unshift()

2. set arguments as the this value of unshift()

3. set 'hello' as the argument to unshift()

---

Array.prototype.unshift.call(arguments, 'hello');

---

As @lonesomeday pointed out, you can use .apply() instead of .call(), but you need to pass an array-like argument as the second argument. So in your case, you'd need to wrap 'hello' in an Array.

Comments

[lonesomeday]

You could also do apply(arguments, ['hello']).

[piotr_cz]

This gives me a strange result in Chrome: ['hello', 'argument1', undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined]