Getting typescript error when pushing object into state array with useState

Question

I want to push new item into my initial state array, using useState hook ,but im getting error: TS2322 Type number is not assignable to type 'never'. ([...pageNumbers, i) underlined

My code:

const [pageNumbers, setPageNumbers] = useState([]);

  for (
    let i = 1;
    i <= Math.ceil(props.totalCommits / props.CommitsPerPage);
    i++
  ) {
    setPageNumbers([...pageNumbers, i]);
  }

tromgy · Accepted Answer · 2021-10-14 21:35:15Z

1

You need to type the state array like this:

const [pageNumbers, setPageNumbers] = useState<Array<number>>([]);

answered Oct 14, 2021 at 21:35

tromgy

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Eddie023 · Accepted Answer · 2021-10-14 21:41:15Z

1

If you don't add a <type> when initializing a empty array, typescript will assume the type as React.SetStateAction<never[]>. So, when you tried to add let i = 1, type number into type never, typescript threw the error Type number is not assignable to type 'never'.

You can assign a type when initializing to fix this issue as following.

 const [pageNumber, setPageNumbers] = useState<number[]>([]);

answered Oct 14, 2021 at 21:41

Eddie023

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