edited

@Sinnbeck Yes, that works when they typing normally on textarea my button is gonna being active, but when right click and pasted text not working.

@MainLess show that Javascript please

@MainLess you can try adding another event listener

document.addEventListener('paste', function(params) {

@Sinnbeck tried this, but still nothing change. When you paste with keyboard (CTRL+V) it's also work fine. But the problem is about the right clicking event.

@MainLess Can you try this simple demo I wrote? It triggers on both for me. Notice that I bound the event to the specific element, not the document

https://jsfiddle.net/qa07pzc9/

You could also consider binding the event to change, so the button is active when you leave the field

@Sinnbeck Your demo work's like a charm, I tried a lot of thing including your demo code, even alert not working :D, and building mix files again but idk what is the problem. But thanks for the effort.

@MainLess did you try binding it directly to the field?

document.getElementById('NewEntryText').addEventListener('paste', function() {
    alert('works')
});

@Sinnbeck Yes, I tried just like your code and build it, still button is disabled.

@MainLess and no alert?

@Sinnbeck Yes, no alert.

@MainLess are there any errors in the browser console? The smallest syntax error can break everything

@Sinnbeck 1-2 small errors but not about our problem.

@MainLess if they are in red, they might break js which means they new code is never being run