# Why do I get 55 when I console this code?

Hello I’m just trying to understand why Im getting 55 as the result from this code Im new lerning while loops, thanks guys

``````var sum =  0;
var num = 0;
while (num <= 10) {
sum += num;
num++;
}
console.log(sum);
``````
``````var sum =  0;
var num = 0;
while (num <= 10) {
sum += num;
num++;
}
console.log(sum);

``````

Here in this code the value of num is updating everytime from 1 to 10.
If you try calculating the loop sum= 0 but num = 1+2+4+5+6+7+8+9+10, you will be getting 55.
To understand it much better try changing the value of this

``````while (num <= 10)
``````

to

``````while (num <= 4)
``````

You’ll get 10, as the value of num gets added.
It works like this

0(sum) = 0 + 1 + 2+ 3+ 4;

2 Likes

Hi,
Initially, the value of `sum` and `num` is `0`.

For every iterations, there’re 2 things happens:

• `num` is added to `sum` ( `sum += num` means `sum = sum + num` )
• `num` increased its value by `1` ( `num++` means `num = num + 1` )

The value of `num` goes from 0 to 1, to 2, to 3 … to 10 then stops.
So `sum = 0 + 1 + 2 + 3 + ... + 10 = 55`.

`55` is the last value of `sum` after the loop ended.

3 Likes
2 Likes

thanks lot this concept its much more clear now

thank you very much toan

thanks for your help very useful