Cannot read properties of null (reading 'querySelector')

# Table of Contents

# Cannot read properties of null (reading 'querySelector')

The "Cannot read properties of null (reading 'querySelector')" error occurs for 2 reasons:

Calling the querySelector() method on a null value (DOM element that doesn't exist).
Inserting the JS script tag above the HTML where the DOM elements are declared.

cannot read property queryselector of null

Here is an example of how the error occurs.

index.js

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const element = null;

// ⛔️ Uncaught TypeError: Cannot read properties of null (reading 'querySelector')
const box = element.querySelector('#box');

Here is another example.

index.js

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const el = undefined;

// ⛔️ Uncaught TypeError: Cannot read properties of undefined (reading 'querySelector')
const box = el.querySelector('#box');

# Make sure the DOM element exists before calling `querySelector`

Make sure you're using the correct id when selecting the DOM element.

The error often occurs after providing an invalid id to the getElementById method.

index.js

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const element = document.getElementById('does-not-exist');
console.log(element); // 👉️ null

// ⛔️ Cannot read properties of null (reading 'querySelector')
const box = element.querySelector('#box');

We provided a non-existent id to the getElementById method, so we got anull value back. Calling the querySelector() method on a null value causes the error.

If you got the error "Cannot read properties of undefined (reading 'querySelector')", you probably used the getElementsByClassName method.

index.js

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const elements = document.getElementsByClassName('does-not-exist');
console.log(elements); // 👉️ []

// ⛔️ Cannot read properties of undefined (reading 'querySelector')
const box = elements[0].querySelector('#box');

We passed a non-existent class name to the getElementsByClassName method, so we got an empty array-like object back.

Trying to access an array at an index out of bounds, returns an undefined value and calling the querySelector method on an undefined value causes the error.

# Place the JS script tag at the bottom of the body tag

Place the JS script tag at the bottom of the body tag.

The JS script should run after the DOM elements are created.

index.html

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<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
  </head>
  <body>
    <!-- ⛔️ BAD - script is run before div exists ⛔️ -->
    <script src="index.js"></script>

    <div id="container">
      <div id="box">Text</div>
    </div>
  </body>
</html>

The JS script tag is placed above the DOM elements it tries to access, so the div element won't be accessible inside the index.js file.

index.js

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const element = document.getElementById('container');
console.log(element); // 👉️ null

// ⛔️ Cannot read properties of null (reading 'querySelector')
const box = element.querySelector('#box');

Instead, place the JS script tag at the bottom of the body, after the DOM elements it tries to access.

index.html

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<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
  </head>
  <body>
    <div id="container">
      <div id="box">Text</div>
    </div>

    <!-- ✅ GOOD - div already exists ✅ -->
    <script src="index.js"></script>
  </body>
</html>

place js script tag at bottom of body tag

Now we can access the div element inside of the index.js file.

index.js

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const element = document.getElementById('container');
console.log(element); // 👉️ div#container

// ✅ Works
const box = element.querySelector('#box');
console.log(box); // 👉️ div#box

calling queryselector method successfully

HTML code is parsed from top to bottom, so the script tag has to come after the DOM elements it needs access to.

# Cannot read properties of null (reading 'querySelectorAll')

The "Cannot read properties of null (reading 'querySelectorAll')" error occurs for 2 reasons:

Calling the querySelectorAll() method on a null value (DOM element that doesn't exist).
Placing the JS script tag above the HTML where the DOM elements are declared.

cannot read property queryselectorall of null

Here is an example of how the error occurs.

index.js

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const el = null;

// ⛔️ Uncaught TypeError: Cannot read properties of null (reading 'querySelectorAll')
el.querySelectorAll('div.box');

Here is another example.

index.js

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const el = undefined;

// ⛔️ Uncaught TypeError: Cannot read properties of undefined (reading 'querySelectorAll')
el.querySelectorAll('div.box');

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

Copied!
const el = document.getElementById('does-not-exist');
console.log(el); // 👉️ null

// ⛔️ Cannot read properties of null (reading 'querySelectorAll')
el.querySelectorAll('div.box');

We passed a non-existent id to the getElementById method and got a null value back. Calling the querySelectorAll() method on a null value causes the error.

If you got the error "Cannot read properties of undefined (reading 'querySelectorAll')", you probably used the getElementsByClassName method.

index.js

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const elements = document.getElementsByClassName('does-not-exist');
console.log(elements); // 👉️ []

// ⛔️ Cannot read properties of undefined (reading 'querySelectorAll')
const boxes = elements[0].querySelectorAll('div.box');

We passed a non-existent class name to the getElementsByClassName() method and got an empty array-like object back.

Accessing an array at an index out of bounds returns undefined. Calling the querySelectorAll() method on an undefined value throws the error.

# Place the JS script tag at the bottom of the body tag

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

Copied!
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
  </head>
  <body>
    <!-- ⛔️ BAD - script runs before div exists ⛔️ -->
    <script src="index.js"></script>

    <div id="container">
      <div class="box">Box 1</div>
      <div class="box">Box 2</div>
    </div>
  </body>
</html>

Notice that the JS script tag is placed above the code that declares the div element. This means that the index.js file cannot access the div element.

index.js

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const el = document.getElementById('container');
console.log(el); // 👉️ null

// ⛔️ Cannot read properties of null (reading 'querySelectorAll')
el.querySelectorAll('div.box');

Instead, you should move the JS script tag to the bottom of the body, after the elements it tries to access.

index.html

Copied!
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
  </head>
  <body>
    <div id="container">
      <div class="box">Box 1</div>
      <div class="box">Box 2</div>
    </div>

    <!-- ✅ GOOD - div already exists ✅ -->
    <script src="index.js"></script>
  </body>
</html>

Now our index.js file has access to the DOM elements.

index.js

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const el = document.getElementById('container');
console.log(el); // 👉️ div#container

// ✅ Works
const boxes = el.querySelectorAll('div.box');
console.log(boxes); // 👉️ [div.box, div.box]

HTML code is parsed from top to bottom, so the script tag has to come after the DOM elements it needs access to.

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Cannot read properties of null (reading 'querySelector')

# Table of Contents

# Cannot read properties of null (reading 'querySelector')

# Make sure the DOM element exists before calling querySelector

# Place the JS script tag at the bottom of the body tag

# Cannot read properties of null (reading 'querySelectorAll')

# Place the JS script tag at the bottom of the body tag

Borislav Hadzhiev

# Make sure the DOM element exists before calling `querySelector`