In TypeScript, you can use the null keyword to declare a variable of the null type. When declared, you can only assign a null value to it. Just like undefined, you can also assign it to a number or boolean value as it is a subtype of all other types:
let nullValue: null = null; let nullableNumeric: number = null; let nullableBoolean: boolean = null;
If a variable is assigned with undefined, then the variable has no value or object assigned to it. However, if a variable is assigned with null, then the variable is a type of an object whose value hasn't been defined.