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

4 votes283 views2 answers
Magento 2 enable template hints command line
TypeScript
2 votes171 views1 answer
Key value pairs typescript
TypeScript
0 vote172 views2 answers
Typescript one of the array items
TypeScript
4 votes203 views1 answer
Firestore decrement
TypeScript
0 vote204 views1 answer
Dotcms elasticsearch query
TypeScript
0 vote174 views1 answer
Typescript import particular class from file
TypeScript
1 vote210 views1 answer
NullInjectorError: R3InjectorError(DynamicTestModule)[AdminTestCentersComponent -> ToastrService -> InjectionToken ToastConfig -> InjectionToken ToastConfig]: NullInjectorError: No provider for InjectionToken ToastConfig!
TypeScript
2 votes174 views1 answer
Aws sts assume-role example
TypeScript
0 vote176 views1 answer
Add multiple constraints in create table sql
TypeScript
10 votes222 views2 answers
Add class to all child elements jquery
TypeScript