How to make TypeScript complain about string concatenation with other type?

Question

Why even in strict mode TypeScript is not complaining about this

Answer 1

Create a type-safe variadic function to do concatenation for you.

concat(...strings: string[]): string {
  var concatenated = "";
  for (var i = 0; i <  strings.length; i++) {
    concatenated += strings[i];
  }
  return concatenated;
};

Now when you concatenate, use your function:

const str: string = '';
const num: object = {};

const result: string = concat(str, num); // throws error

Example here