JavaScript redirect is getting "hijacked" and it is not onbeforeunload event.

My redirect in javascript somehow gets "hijacked" and I don't understand how.

Previous developer (who is no longer working with the company) on page load initialized onbeforeunload event like so:

window.onbeforeunload = function() {
    if(<some condition>)
        <make some ajax request>
}

Now I have a requirement where I need to do a redirect, like so:

window.location = "https://duckduckgo.com"; // just some external url

Both pieces of code above are being reused by multiple pages. In all pages redirect works, except one. Only on 1 page after my debugger steps over my redirect and then reaches this point

    window.onbeforeunload = function() {
        if(<some condition>)
            <make some ajax request>
--> }

I do a step over and instead of getting redirected to https://duckduckgo.com I get redirected to a different internal page in my application.

Looks like something is happening in javascript between onbeforeunload and my redirect but I can't understand what it is. I don't even understand how I can continue debugging this.

- How is that possible?

- What can I do to debug this farther?

- Is there some kind of onbeforebeforeunload event or something?

Update.

"onbeforeunload" and "redirect" snippets of code are located in two different files, kind of like so:

File A.js:

$(function(){
    ...
    window.onbeforeunload = function() {
        if(<some condition>)
            <make some ajax request>
    }
    ...
});

File B.js

var Obj1 = (function(){
    return {
        init(): function() {
            this.Obj2.init();
        }
    }
});

Obj1.Obj2 = (function(){
    var process = function(){
        ...
        window.location = "https://duckduckgo.com";
        ...
    }
    return {
        run: process,
        init: function(){
            ...
        }
    }
});

and then at some point process function gets called:

Obj1.Obj2.run();

Update 2:

I put debugger; in and out of every single piece of code where I saw "beforeunload" like so in my entire project:

$(this).on("beforeunload", function(){
    ...
});

Not a single breakpoint got hit.

Update 3.

I added the following lines of code prior to redirect:

window.onunload = function(){
    debugger; // Not hit
};
window.onbeforeunload = function(){
    debugger; // <-- Hit 1st
};
$(window).on("beforeunload", function() {
    debugger; // <-- Hit 2nd
});
$(window).on("unload", function() {
    debugger; // Not hit
});
window.location = "https://<url>";

As comments above describe, first window.onbeforeunload gets hit, then $(window).on("unload"... and then redirect to internal (not the one that I need) page happens.

posted 9 months ago

CC BY-SA 4.0

9mo ago

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