To solve the "Cannot read property 'offsetTop' of null" error, make sure the id you're using to get the element is contained in the DOM. The error often occurs after providing a non-existent `id` to the `getElementById` method.

Solve - Cannot read property 'offsetTop' of Null in JS

## Solve - Cannot read property 'offsetTop' of Null

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

1. Accessing the `offsetTop` property 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.

```javascript:index.js
const el = null;

// ⛔️ Cannot read properties of null (reading 'offsetTop')
console.log(el.offsetTop);
```

**To solve the "Cannot read property 'offsetTop' of null" error, make sure the
`id` you're using to get the element is contained in the DOM. The error often
occurs after providing a non-existent `id` to the `getElementById` method.**

```javascript:index.js
const el = document.getElementById('does-not-exist');
console.log(el); // 👉️ null

// ⛔️ Cannot read properties of null (reading 'offsetTop')
console.log(el.offsetTop);
```

We provided a non-existent `id` to the `getElementById` method and got a `null`
value back.

Accessing the `offsetTop` property on a `null` value causes the error.

**To solve the "Cannot read property 'offsetTop' 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.**

```html:index.html
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
  </head>
  <body>
    
    <script src="index.js"></script>

    <div id="box">Content here</div>
  </body>
</html>
```

We placed the JS script tag at the top of the body tag. The `index.js` file is
executed before the `div` element is available, therefore the `div` can't be
accessed from the file.

```javascript:index.js
const el = document.getElementById('box');
console.log(el); // 👉️ null

// ⛔️ Cannot read properties of null (reading 'offsetTop')
console.log(el.offsetTop);
```

Instead, move the JS script tag to the bottom of the body tag, after all the DOM
elements the file tries to access.

```html:index.html
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
  </head>
  <body>
    <div id="box">Content here</div>

    
    <script src="index.js"></script>
  </body>
</html>
```

Now we are able to access the `div` element inside of the `index.js` file.

```javascript:index.js
const el = document.getElementById('box');
console.log(el); // 👉️ div#box

// ✅ Works
console.log(el.offsetTop); // 👉️ 8
```

## Conclusion

The "Cannot read property 'offsetTop' of null" error occurs when trying to
access the `offsetTop` property on a `null` value.

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

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Solve - Cannot read property 'offsetTop' of Null in JS

Solve - Cannot read property 'offsetTop' of Null #

Conclusion #

Borislav Hadzhiev

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Solve - Cannot read property 'offsetTop' of Null in JS