Create a reset of javascript Array prototype when Array.prototype has been modified?

OP’s probably already figured something out by now, but for anyone else coming in from a Google search or wherever, here’s a function that returns the unmodified version of any default constructor passed to it:

// Note: the double name assignment below is intentional.
// Only change this part if you want to use a different variable name.
//  │││││ The other one here needs to stay the same for internal reference.
//  ↓↓↓↓↓            ↓↓↓↓↓
var reset = function reset(constructor) {
    if (!(constructor.name in reset)) {
        var iframe = document.createElement('iframe');
        iframe.src="https://stackoverflow.com/questions/13990187/about:blank";
        document.body.appendChild(iframe);
        reset[constructor.name] = iframe.contentWindow[constructor.name];
        document.body.removeChild(iframe);
    } return reset[constructor.name];
}

---

Usage goes like this:

The Problem

Somebody does something stupid to a default prototype…

Array.prototype.push = function () {
    var that = this;
    [].forEach.call(arguments, function (argument) {
        that.splice(Math.round(Math.random()*that.length), 0, argument)
    }); return 'Trolololo';
}

…and your code becomes a broken mess.

var myArray = new Array(0, 1, 2, 3);
//-> undefined
    // Ok, I made an array.
myArray;
//-> [0, 1, 2, 3]
    // So far so good...
myArray.push(4, 5);
//-> "Trolololo"
    // What?
myArray;
//-> [5, 0, 1, 2, 4, 3]
    // WHAT!?

The Solution

So you throw that function into the mix…

var reset = function reset(constructor) {
    if (!(constructor.name in reset)) {
        var iframe = document.createElement('iframe');
        iframe.src="https://stackoverflow.com/questions/13990187/about:blank";
        document.body.appendChild(iframe);
        reset[constructor.name] = iframe.contentWindow[constructor.name];
        document.body.removeChild(iframe);
    } return reset[constructor.name];
}

…and put it to use like so.

var myArray = new reset(Array)(0, 1, 2, 3);
//-> undefined
    // Looks the same
myArray;
//-> [0, 1, 2, 3]
    // Still looks the same
myArray.push(4, 5);
//-> 6
    // Hey, it returned what it's supposed to...
myArray;
//-> [0, 1, 2, 3, 4, 5]
    // ...and all's right with the world again!

Also, because each reset constructor is cached the first time it’s returned, you can save a character if you want to by referencing the cache directly (reset.Array) instead of through the function (reset(Array)) every time after that.

---

Good luck!