How to bind multiple actions to a keyboard event [duplicate]

Question

I am trying to make a chrome extension that modifies the text in an active text area of a Facebook chat window. But I want the change to take place only when the user presses the enter key so that the text doesn't change while it is still in the textarea. I want it to happen using javascript and make it feel like it's happening in the background although I want it to get triggered on the keydown event of the enter key.

Now the relevant JavaScript for the chat window's textarea in Facebook is:

<textarea class="blah" 
onkeydown="window.Bootloader && Bootloader.loadComponents(["control-textarea"], 
function() { TextAreaControl.getInstance(this) }.bind(this)); ">
</textarea>

And in my extension's JavaScript file. I bind the keydown event using something like this:

//elem is bound to the focussed textarea object
elem.onkeydown = function(evt) {
              if(evt.keyCode == 13){
                 //Some javascript code I want to execute here...
               }
        };  

I think as soon as the user presses the enter key, the textarea is cleared and some sort of a post request is made. So I lose the scope of the text I wanted to modify using JavaScript. I checked that the enter key binding is working for my extension by pressing shift + enter, and it modified the text without a problem. So my script is working fine.

However I want my script to be executed before the textarea is cleared and the post request is made. I just don't want the user to see the text getting modified.

Can I add/modify the keybinding of the textarea used by Facebook as shown above in my script for the google chrome extension? Any help is deeply appreciated.

Answer 1

There are a million duplicates of this question on here, but here goes again anyway:

You can use target.addEventListener(type, listener[, useCapture]); In your case, it would be

document.addEventListner(keypress, function(event) { //You can use keydown too
  if (event.which === 13) { // Value for Enter key if keydown or keyup used, use event.keyCode
    //some code that you want to add
  }
}  

If you are using jQuery, you can use

$(document).keypress(function(event){
 if (event.which === 13) { 
   // Your code here
 }
});

P.S. - In case of adding crossbrowser support, you should use something like this:-

if (target.addEventListener) {
  target.addEventListener('keypress',myFunction,false);
} 
else if(target.attachEvent) {
  target.attachEvent('onkeypress', myFunction, false);
} else {
  target.onkeypress = myFunction;
}
// Here myFunction is the callback where you would check for the character code and your custom code