How is the js for loop sum 55 and not 45?

Question

let sum = 0;
for (let i = 0; i <= 9; i++, sum += i);
console.log(sum);

Answer 1

richard honour

If you do like that inside loop then both i++, sum += i will work same time but if you do like this then sum += i will work after checking condition so sum will be only 45.

let sum = 0;
for (let i = 0; i <= 9; i++) {
sum += i;
}
console.log(sum);//45

Answer 2

richard honour

Because we are doing sum += i after i++ so when i <= 9 will be true then after i++, sum = 45 + 10 = 55

Answer 3

Thanks never thought bout it that way... ☺