Какие типы данных могут быть null или undefined в Typescript?

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let myVar: string | null;
myVar = "hello"; // OK
myVar = null; // OK

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function myFunc(): void {
  // do something
  return undefined;
}

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let myObj: object | null;
myObj = {name: "John"}; // OK
myObj = null; // OK

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class MyClass {
  myProp?: string;
  myMethod?(): void {
    // do something
  }
}

const myInstance = new MyClass();
myInstance.myProp = "hello"; // OK
myInstance.myProp = null; // OK
myInstance.myMethod = undefined; // OK