Javascript HTML5 Capture keyCode and write to Canvas

Russell picture Russell · Sep 16, 2010 · Viewed 10.3k times · Source

I'm writing an application in which I need to simulate a textarea. The only way I know how to approach it is to capture the keyCode on a key event. How would one go about taking that keyCode and, supporting utf-8, apply that to the canvas?

Cheers

Answer

Tim Down picture Tim Down · Sep 16, 2010

This seems like a bad idea since there is an awful lot over and above text input that a textarea gives you for free (caret, selection, cut, paste, drag and drop, arrow key handling, etc.), but here's two things you need to do :

  1. Give your <canvas> a tabindex attribute so that it may receive focus and hence raise key events;
  2. Add a keypress (not keydown) handler to the <canvas> element to capture text input.

Code:

<canvas id="textarea" tabindex="1" width="300" height="200"></canvas>

<script type="text/javascript">
   var el = document.getElementById("textarea");
   el.onkeypress = function(evt) {
       var charCode = evt.which;
       var charStr = String.fromCharCode(charCode);
       alert(charStr);
   };
</script>