In Typescript how do you type for (const element of elements ) {}

Question

I tried

for (const element as ElementType of elements ) {}

or

for (const element of elements as ElementType) {}

Both are incorrect.

Answer 1

You dont have to do anything.

interface TestElement {
    id: Number;
}

const arr: TestElement[] = [];

for (const element of arr ) {
    element // It is implicitly cast to TestElement
}

Answer 2

I'm not sure why Typescript doesn't allow type annotations or type assertions on variables like this in for/of loops. You can achieve something similar by asserting the type of the array, rather than the element:

let arr: any = [1, 2, 3, 4];

for (let x of (arr as number[])) {
    x // number
}

It's a bit messy because of the extra brackets, but it does the job.

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