Narrow with an Aliased Union

Sometimes you want a function to accept more than one type but still return a consistent result. Instead of repeating string | number everywhere, you can alias the union type. You can use typeof to narrow to the correct branch and handle each case.

// Alias the union type
type StringOrNum = string | number;

function toLength(value: StringOrNum): number {
  if (typeof value === "string") {
    return value.length; // here it's type string
  }
  return value; // here it's type number
}

Your Task

1. Define type Input = string | number.
2. Implement toNumber(x: Input): number that returns:

• the value itself when x is a number
• parseFloat(x) when x is a string (assume valid numeric strings).