function mult(...args) {
	// base case
  // 	all recursive functions should have a base case so they don't run forever
	if (args.length <= 2) {
		return args[0] * args[1];
	}
	// recursive (reductive) call
	return args[0] * mult(...args.slice(1));
}

mult(3,4,5);	// 60

mult(3,4,5,6);	// 360

Note: ​.slice​ does not mutate the array. It creates a new array.This is not proper tail call since calling ​mult​ is not the last expression there's a multiplication after that.