// Practical example
//https://www.typescriptlang.org/docs/handbook/advanced-types.html#union-types
function padLeft(value: string, padding: string | number) {
    if (typeof padding === "number") {
        return Array(padding + 1).join(" ") + value;
    }
    if (typeof padding === "string") {
        return padding + value;
    }
    throw new Error(`Expected string or number, got '${padding}'.`);
}

console.log(padLeft('hello', 'world')); //'worldhello'
console.log(padLeft('hello', 10)); //                   hello
// console.log(padLeft('hello', true)); //Fails to compile