Get string value or first element of array as string

Have the following function:

function x(p: string | string[]): string | string[];

How do I ensure that the following just outputs a single string value?

console.log(x());

I.e.:

console.log(x("Hello")); // should be "Hello"
console.log(x(["Hello", "World"])); // should be "Hello"

Any shortcut in JavaScript?

>Solution :

like this:

function x(p:string|string[]){
 return Array.isArray(p)?p[0]:p
}