How to persuade typescript to accept that array isn't empty?

Question

I have simple code construction:

const arr: number[] = [1];
while (arr.length > 0) {
   const current: number = arr.pop();
   ...
}

Typescript argues (to "const cutrent") that "Type 'number | undefined' is not assignable to type 'number'" Obviously from condition of "while" that the variable "current" is always number (not undefined). How to explain it to typescript without ugly work arounds?

Does this answer your question? Typescript: Type 'string | undefined' is not assignable to type 'string' — Tobias S.
– Tobias S., Commented Oct 16, 2022 at 17:09

MPCL5 · Accepted Answer · 2022-10-16 17:00:35Z

3

Try this:

const current: number = arr.pop() as number;

answered Oct 16, 2022 at 17:00

MPCL5

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