Typescript assert non null

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();
}

Source: stackoverflow.com

Similar codes

3 votes269 views3 answers
How to view documents folder simulator swift
TypeScript
2 votes354 views1 answer
'mat-checkbox' is not a known element
TypeScript
0 vote284 views1 answer
Angular redirect on submit
TypeScript
0 vote269 views1 answer
Grid layout elements in one row
TypeScript
0 vote275 views1 answer
What is use hsts in .net core
TypeScript
0 vote268 views1 answer
Acces arrey lements without comma
TypeScript
0 vote277 views1 answer
W to check whether an image is a broken image or not in typescript angular
TypeScript
0 vote266 views1 answer
What are the testing types
TypeScript
0 vote246 views1 answer
Typescript dynamic array key
TypeScript
0 vote283 views1 answer
Pandas value_counts multiple columns
TypeScript