Borislav Hadzhiev
Last updated: Jul 25, 2022
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The "setAttribute is not a function" error occurs for multiple reasons:
setAttribute()
method on a value that is not a DOM element.setAttribute
method on a jQuery object (should use attr()
instead).If you use jQuery, use the attr()
method instead of setAttribute
.
const box = $('#box'); console.log(box); // ✅ works box.attr('id', 'first');
Here is an example of how the error occurs in JavaScript.
<!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>
index.js
file.Here is the code in index.js
.
const boxes = document.querySelectorAll('.box'); console.log(boxes); // 👉️ [div.box, div.box, div.box] // ⛔️ Uncaught TypeError: boxes.setAttribute is not a function boxes.setAttribute('id', 'first');
We called the
Element.setAttribute
method on a NodeList
and not a DOM element, which caused the error.
To solve the "setAttribute is not a function" error, make sure to only call
the setAttribute
method on valid DOM elements and place the JS script tag at
the bottom of the body, after the DOM elements have been declared.
const boxes = document.querySelectorAll('.box'); console.log(boxes); // 👉️ [div.box, div.box, div.box] // ✅ Works boxes[0].setAttribute('id', 'first');
By accessing the element at index 0
of the NodeList
, we got back a DOM
element, on which we can safely call the setAttribute
method.
setAttribute
method.For example, a basic DOM element has a type of object, so we can check if the
value is an object and contains the setAttribute
property before calling the
method.
const box = null; if (typeof box === 'object' && box !== null && 'setAttribute' in box) { box.setAttribute('id', 'example'); }
Our if
condition uses the logical AND (&&) operator, so for the if
block to
run, all 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 with console.log(typeof null)
, you will get an
"object"
value back, so we have to make sure the value is not null
.
setAttribute
property.Then we know we can safely call the setAttribute
method on the object.
This approach is called duck-typing.
When using duck-typing, we simply check if the object implements specific properties or methods and if it does, we assume it's an object of the correct type.