Typescript check if object or string

Below is the code to detect whether a given object or a string is a string type object in TypeScript:

checkForString(obj: any) {
    return obj instanceof String || typeof obj === 'string';
}

Examples of results based on above code:

this.checkForString('Hello World');
true

this.checkForString({});
false

this.checkForString({message:'Hello World'});
false