Adding data to an existing function dynamically

Question

I was wondering if we can add data to a function which is already defined in Javascript.

    var win;
    window.onload= function()
    {

        win = window.onbeforeunload;
        win = win.toString();

        var firstLetter = win.indexOf('{');


        win = win.substring(firstLetter + 1, win.length - 1);
        //Getting the data of the function [firstLetter = first occurrence of { ]

        win = win + 'alert("More Unload");';

        `/* Here, I want to rebind var win to the window.onbeforeunload event*/`
    }   

    window.onbeforeunload = function () 
    {
        alert("Unload function");
        alert("More Unload");
    }

Is this possible?

Thanks.

ThiefMaster · Accepted Answer · 2011-11-25 09:42:43Z

1

You can create a function using new Function(yourCodeString).

However, this kind of code rewriting is extremely messy and if you need it you are doing something wrong for sure!

answered Nov 25, 2011 at 9:42

ThiefMaster

320k85 gold badges608 silver badges648 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Jayesh Over a year ago

Ok. See I am writing a plugin that has an onbeforeunload function. I want to be sure that my onbeforeunload doesn't collide if there is one on the page where my plugin would be integrated.

ThiefMaster Over a year ago

At least firefox doesn't even show the message provided in onbeforeunload. And using alert() in that function sounds super-annoying since it will be two popups the user will have to click away.

Collectives™ on Stack Overflow

Adding data to an existing function dynamically

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related