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typescript assert non null

Awful Ape answered on January 4, 2021 Popularity 9/10 Helpfulness 2/10

answer typescript assert non null

typescript assert non null

Comment

interface Foo { bar(): void }
declare function getFoo(): Foo | undefined;

function assert(value: unknown): asserts value {
    if (value === undefined) {
        throw new Error('value must be defined');
    }
}

function test() {
    const foo = getFoo();
    // foo is Foo | undefined here
    assert(foo);
    // foo narrowed to Foo
    foo.bar();
}

Popularity 9/10 Helpfulness 2/10 Language typescript

Source: stackoverflow.com

Tags: assert null typescript

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