I am using useRef, and accessing its child elements.
And I am getting this error.
Element implicitly has an 'any' type because expression of type 'number' can't be used to index type '{}'. No index signature with a parameter of type 'number' was found on type '{}'
The code is
const subCnt = useRef<HTMLDivElement>();
useEffect(()=>{
if (!(subCnt.current?.children?.length! > 0)) return
let lastChild: ReactNode = subCnt.current?.children;
lastChild = lastChild[lastChild?.length - 1]; //Getting the error here
...
})
The Line I am getting the error is at lastChild = lastChild[lastChild?.length - 1];
Why is it showing this error?
Juan Pablo Isaza
Your actual mistake is on the line before:
let lastChild: ReactNode = subCnt.current?.children;
I don't know why TypeScript doesn't complain, apparently the types are weirdly compatible, but they really ought not. The type of .children is HTMLCollection - and it contains all children, not only the last one, so the name is confusing as well.
The correct way to do it would be
useEffect(() => {
const children: HTMLCollection | undefined = subCnt.current?.children;
if (!children?.length) return;
const lastChild: HTMLElement = children[children.length - 1];
…
})
but you can actually simplify that by simply using .lastElementChild directly:
useEffect(() => {
const lastChild: HTMLElement | undefined = subCnt.current?.lastElementChild;
if (!lastChild) return;
…
})