Borislav Hadzhiev
Fri Mar 25 2022·2 min read
Photo by Paul Gilmore
The error "Property 'style' does not exist on type 'Element'" occurs when we
try to access the style
property on an element that has a type of Element
.
To solve the error, use a type assertion to type the element as HTMLElement
before accessing the property.
This is the index.html
file for the examples in this article.
<!DOCTYPE html> <html> <head> <meta charset="UTF-8" /> </head> <body> <div id="box">Hello world</div> <script src="./src/index.ts"></script> </body> </html>
And here is an example of how the error occurs in the index.ts
file.
// 👇️ const box: Element | null const box = document.querySelector('#box'); if (box != null) { // ⛔️ Property 'style' does not exist on type 'Element'.ts(2339) box.style.backgroundColor = 'salmon'; }
The reason we got the error is because the return type of the
document.querySelector
method is Element | null
and the
style
property doesn't exist on the Element
type.
To solve the error, use a type assertion to type the element as an
HTMLElement
.
const box = document.querySelector('#box') as HTMLElement | null; if (box != null) { box.style.backgroundColor = 'salmon'; }
If you used the
document.getElementsByClassName
method, type the collection as HTMLCollectionOf<HTMLElement>
.
// 👇️ with getElementsByClassName // type as HTMLCollectionOf<HTMLElement> const boxes = document.getElementsByClassName( 'box', ) as HTMLCollectionOf<HTMLElement>; for (let i = 0; i < boxes.length; i++) { boxes[i].style.backgroundColor = 'salmon'; }
We could have also used the more specific HTMLDivElement
type, because we are
typing a div
element.
Type assertions are used when we have information about the type of a value that TypeScript can't know about.
box
variable stores anHTMLElement
or a null
value and not to worry about it.We used a
union type
to specify that the variable could still be null
, because if an HTML element
with the provided selector does not exist in the DOM, the querySelector()
method returns a null
value.
We used a simple if
statement that serves as a
type guard
to make sure the box
variable doesn't store a null
value before accessing
its style
property.
// 👇️ const box: Element | null const box = document.querySelector('#box') as HTMLElement | null; // 👉️ box has type Element or null here if (box != null) { // 👉️ box has type Element here box.style.backgroundColor = 'salmon'; }
box
variable has a type of HTMLElement
in the if
block and allows us to directly access its style
property.It's always a best practice to include null
in the type assertion, because the
querySelector
method would return null
if no element with the provided
selector was found.