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JavaScript

Brian CI
Brian CI
28,971 Points
Posted by Brian CI
Brian CI
28,971 Points

TypeError: myDiv is null

I'm trying to follow the Javascript Foundations course but I am getting an error even though I think I've copied the code the exactly.

I am using firefox instead of chrome. Is it possible firefox gives errors where chrome does not? Seems unlikely.

My relevant code:

var color = "red";

var myDiv = document.getElementById('myDiv');
myDiv.style.background = "black";
myDiv.style.color = "#ffffff";

5 Answers

Brian CI
Brian CI
28,971 Points
Brian CI
Brian CI
28,971 Points

D'oh. I think I see it now. I didn't remove the line above when the tutorial said to move it down lower. So one is making the error and one is working. D'oh!

dan schmidt
dan schmidt
2,576 Points
dan schmidt
dan schmidt
2,576 Points

Yea, I see what was happening. Any javascripts that are included in the head of your document will be executed before the DOM has been populated by your browser. If want to ensure that your javascript is executed after the browser is finished rendering your page, you would assign it to the window.onload event:

window.onload = function (e) {

     /* your code here */

};
dan schmidt
dan schmidt
2,576 Points
dan schmidt
dan schmidt
2,576 Points

The problem has to be with the id. Either it is misspelled in the html or has been declared as a class instead of an id. Without seeing your code, that is as much as I can speculate.

Brian CI
Brian CI
28,971 Points
Brian CI
Brian CI
28,971 Points

See code below

Brian CI
Brian CI
28,971 Points
Brian CI
Brian CI
28,971 Points

See code below

Brian CI
Brian CI
28,971 Points
Brian CI
Brian CI
28,971 Points 
<!DOCTYPE html>
<html lang="en">
  <head>
    <title> JavaScript Foundations: Variables</title>
    <style>
    html {
        background: #FAFAFA;
        font-family: sans-serif;
    }
    </style>
    <script src="jsFoundationsVariables.js"></script>
  </head>

  <body>
        <h1>JavaScript Foundations</h1>
        <h2>Variables</h2>

        <div id="myDiv">
        This is a div with the id of "myDiv"
        </div>
        <script src="jsFoundationsVariables.js"></script>
  </body>
</html>

/* JavaScript Foundations: Variables */

var color = "red";

var myDiv = document.getElementById('myDiv');
myDiv.style.background = "black";
myDiv.style.color = "#ffffff";