CODEWITHSUNDEEP
javascriptfunction
Moon
Moon

Reputation: 22605

How to recover overwritten native methods?

I'm working on a project and noticed that one of the core developers overwrote alert() method in his JS.

Is it possible to recover it without asking/changing his code?

He did something like..

function alert() {
   // his code
}

Upvotes: 0

Views: 341

Answers (2)

Hamish
Hamish

Reputation: 23346

If you can inject code before the code that's causing this problem, you can "fix" it:

E.g.

window._alert = window.alert;
// bad code ..
window.alert = function() {};
// restore correct function
window.alert = window._alert;

Of course, that means that the other code might now function incorrectly or cause unwanted alert boxes.

It also depends on how exactly the other code is overwriting alert. If it's just sloppy code where a function called alert is being hoisted to the global scope by mistake, you potentially fix it by wrapping the whole codeblock in an anonymous function:

(function() {
    // scope to this block
    var alert;

    // bad code here
    alert = function() {};
})();
// alert doesn't pollute global scope:
alert("HI");

Upvotes: 2

Ry-
Ry-

Reputation: 225125

You can make an intermediate <iframe>.

var f = document.createElement("iframe");
f.width = 0;
f.height = 0;
f.src = "about:blank";
f.onload = function() {
    f.contentWindow.alert("Hi!");
    document.body.removeChild(f);
};
document.body.appendChild(f);

Don’t make an intermediate <iframe>.

Upvotes: 6

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