How to sum up all numbers entered in prompt

var num = prompt("Enter a number");

for (var sum = 0; sum <= num; sum++) {
  sum = sum + 1;
}
document.write(sum);

example when I enter 6 in the prompt it will sum 1+2+3+4+5+6 =21. but as of right now i can only print 123456 instead of 21.

>Solution :

The problem with your code is that you’re using sum for the loop and for the answer. That’s messing everything up. You can use a variable for the loop and another variable for the sum.

Maybe that works for you.

var num = prompt("Enter a number");
var sum = 0;
for(var i = 1; i <= num; i++) {
    sum += i;
}
document.write(sum);