Solve - Cannot read property 'focus' of Null in JavaScript

avatar

Borislav Hadzhiev

Thu Oct 21 20212 min read

Solve - Cannot read property 'focus' of Null #

The "Cannot read property 'focus' of null" error occurs for 2 reasons:

  1. Calling the focus() method on a null value (DOM element that doesn't exist).
  2. Placing the JS script tag above the HTML where the DOM elements are declared.
index.js
const el = null; // โ›”๏ธ Cannot read properties of null (reading 'focus') el.focus();

To solve the "Cannot read property 'focus' of null" error, make sure the id you're using to get the element exists in the DOM. The error often occurs after providing an invalid id to the getElementById method.

index.js
const el = document.getElementById('does-not-exist'); console.log(el); // ๐Ÿ‘‰๏ธ null // โ›”๏ธ Cannot read properties of null (reading 'focus') el.focus();

We passed an id that doesn't exist to the getElementById method and got a null value back.

Calling the focus() method on a null value causes the error.

To solve the "Cannot read property 'focus' of null" error, place the JS script tag at the bottom of the body tag. The script should run after the DOM elements have been created.

index.html
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8" /> </head> <body> <!-- โ›”๏ธ BAD - script is ran before input exists โ›”๏ธ --> <script src="index.js"></script> <input type="text" id="first_name" value="John" /> </body> </html>

The JS script tag is placed above the input element, therefore the index.js file is executed before the input element is present in the DOM.

index.js
const el = document.getElementById('first_name'); console.log(el); // ๐Ÿ‘‰๏ธ null // โ›”๏ธ Cannot read properties of null (reading 'focus') el.focus();

The JS script tag should be placed at the bottom of the body tag, after the elements the file tries to access.

index.html
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8" /> </head> <body> <input type="text" id="first_name" value="John" /> <!-- โœ… GOOD - input already exists โœ… --> <script src="index.js"></script> </body> </html>

Now we have access to the input element in the index.js file.

index.html
const el = document.getElementById('first_name'); console.log(el); // ๐Ÿ‘‰๏ธ input#first_name // โœ… Works el.focus();

Conclusion #

The "Cannot read property 'focus' of null" error occurs when trying to call the focus() method on a null value.

To solve the error, run the JS script after the DOM elements are available and make sure you only call the method on valid DOM elements.

Join my newsletter

I'll send you 1 email a week with links to all of the articles I've written that week

Buy Me A Coffee