Question

I have a javascript code that points to an image using getElementById. But when I debug it in firebug, it says that my variable has a value of “null”. Here is my code:

var image = document.getElementById('myImage');

image.src = "imageone.png";

Answer 1

That’s because there is no element with that id.

If the element actually have that id, then the reason is that the element hasn’t been parsed yet when the code runs. Put it in the load event to run it after the entire page has been parsed:

window.onload = function() {
  var image = document.getElementById('myImage');
  image.src = "imageone.png";
};

Alternatively, you can put the script block in the body element, below the image tag.