Factorisation of a digit in javascript

factorise.js

function factorialize(num) {
		  //check if num == 0
			if (num === 0) {
			return 1;
		  }
		  //else calculate factorial
		  return num * factorialize(num - 1);
		  }
    //calling the function. this will return 120
		factorialize(5);