Null and Undefined

Nullable types make missing values explicit so code can handle them before use.

nullable.ts

function labelName(name: string | null): string {
    if (name === null) {
        return "anonymous";
    }
    return name.toUpperCase();
}

const nickname: string | null = ;
const label: string = labelName(nickname);

console.log(`name=${label}`);

function labelName(name: string | null): string {
    if (name === null) {
        return "anonymous";
    }
    return name.toUpperCase();
}

const nickname: string | null = ;
const label: string = labelName(nickname);

console.log(`name=${label}`);

function labelName(name: string | null): string {
    if (name === null) {
        return "anonymous";
    }
    return name.toUpperCase();
}

const nickname: string | null = ;
const label: string = labelName(nickname);

console.log(`name=${label}`);

nullable value A nullable type such as `string | null` says the value might be present or intentionally empty.