How to type the input parameters of a function, which can change during the check?

Question

typescript

there is some function that can take an object or an array of these objects.
on initial argument check, if not an array wraps the object in an array.
ts swears at the whole thing.
Whether probably this business to make friends without the declaration of a new variable?

fn(x: any, y: any, z: any):any{
    if (!Array.isArray(x)) x = [x];
    if (!Array.isArray(y)) y = [y];
    if (!Array.isArray(z)) z = [z];
// .....
}

Answer 1

For example:

function fn(x: number | Array<number>): void {
    if(!Array.isArray(x))
        x = [x];
    console.log(x);
}

In your code, the compiler most likely swears that xs is not declared anywhere