Solve - getBoundingClientRect is not a function Error in JS

Solve - getBoundingClientRect is not a function Error #

The "getBoundingClientRect is not a function" error occurs for multiple reasons:

calling the getBoundingClientRect() method on a value that is not a DOM element.
placing the JS script tag above the code that declares the DOM elements.
misspelling getBoundingClientRect (it's case sensitive).

getboundingclientrect is not a function

Here is an example of how the error occurs.

index.html

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<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
  </head>

  <body>
    <div class="box">Box 1</div>
    <div class="box">Box 2</div>
    <div class="box">Box 3</div>

    <!-- ✅ Your JS script here ✅ -->
    <script type="module" src="index.js"></script>
  </body>
</html>

Notice that the JS script tag is placed at the bottom of the body tag. Had we placed the JS script tag above the code that declares the DOM elements, they wouldn't be accessible in the index.js file.

And here is the related JavaScript code.

index.js

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const boxes = document.getElementsByClassName('box');

// ⛔️ TypeError: boxes.getBoundingClientRect is not a function
const result = boxes.getBoundingClientRect();

We called the Element.getBoundingClientRect() method on a NodeList and not a DOM element, so we got the error back.

To solve the "getBoundingClientRect is not a function" error, make sure to only call the getBoundingClientRect method on valid DOM elements and place the JS script tag at the bottom of the body, after the DOM elements have been declared.

index.js

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const boxes = document.getElementsByClassName('box');

const result = boxes[0].getBoundingClientRect();

// 👇️ {bottom: 26.87..., height: ..., left: ..., right: ...}
console.log(result);

By accessing the element at index 0 of the NodeList, we got back a DOM element, on which we can safely call the getBoundingClientRect method.

If the element you're calling the method on sometimes does not exist, you can conditionally check if the element is there before calling the getBoundingClientRect method on it.

For example, a basic DOM element has a type of object, so we can check if the value is an object and contains the getBoundingClientRect property before calling the method.

index.js

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const box = null;

if (typeof box === 'object' && box !== null && 'getBoundingClientRect' in box) {
  const result = box.getBoundingClientRect();
  console.log(result);
}

Our if condition uses the logical AND (&&) operator, so for the if block to run, all of the conditions have to be met.

We first check if the box variable stores a value with a type of object because DOM elements have a type of object.

Then we check if the variable is not equal to null. Unfortunately, if you check the type of null - console.log(typeof null), you will get an "object" value back, so we have to make sure the value is not null.

The last thing we check for is that the object contains the getBoundingClientRect property.

Then we know we can safely call the getBoundingClientRect method on the object.

If the error persists, make sure you're not misspelling getBoundingClientRect as it is case sensitive and quite tricky to spell.

You can also console.log the value you're calling the method on and make sure it's a valid DOM element.

Solve - getBoundingClientRect is not a function Error in JS

Solve - getBoundingClientRect is not a function Error #

Further Reading #

Borislav Hadzhiev