延迟事件处理程序直到另一个函数完成

Question

We've recently implemented a 3rd party solution into our website, for which I can not directly update the code but I can add my own javascript to manipulate it. This solution has a button, which triggers an AJAX request. I would like to run some custom code of my own before that AJAX request is submitted and only submit it if my code allows it.

Is there a way I can store the click eventhandler of that button in a variable or another function before overwriting the binding with my own function that will then trigger the original eventhandler function once mine has completed?

Hope that's clear...

EDIT: The click handler is added in the 3rd parties solution like so, fairly standard really. However I can not directly access the controller being used so I can't just copy the function. Also the service provider occasionally updates their code so if I copied it, it wouldn't update when they update their code.

Answer 1

This solution has a button, which triggers an AJAX request. I would like to run some custom code of my own before that AJAX request is submitted and only submit it if my code allows it.

Without diving into jQuery's event handler management internals (which can change at any time), probably the simplest thing is to hide the button and replace it with your own, then trigger the button when appropriate. See comments:

 // === The original handler $("#the-btn").on("click", function() { console.log("Original handler ran"); }); // === Your code // Get and hide the original button var btn = $("#the-btn"); btn.hide(); // Create and add replacement var newBtn = $("<input type=button>"); newBtn.val(btn.val()); newBtn.on("click", function() { console.log("Your handler starting (I'm assuming an async process)..."); setTimeout(function() { console.log("Your handler is done, triggering original"); btn.click(); }, 800); }); newBtn.insertBefore(btn);

 <input type="button" id="the-btn" value="Do Something"> <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>