This code is from a Javascript book but when i tested in Visual Stuido Code it does not work as the book described. Why?

Quote from book: “In the first alert box, you will see num1= 3 result= 3. Since the ++ operator is used before the operand here, the value of num1 is increased by 1 and then assigned to the result variable. In the second alert box, you will see num1= 3 result= 2. This is because the ++ operator is used after the operand, so the value of num1 is increased after it has been assigned to the result variable. The result variable gets a value of 2, but num1 will be increased to 3.”