Problem

Just solved Euler Project Problem 2 using JavaScript and I would like to know how I could improve my code. I do think it looks good, but you never know.

### Problem Statement

Each new term in the Fibonacci sequence is generated by adding the

previous two terms. By starting with 1 and 2, the first 10 terms will

be:

`1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...`

By considering the terms in the Fibonacci sequence whose values do not

exceed four million, find the sum of the even-valued terms.

```
function fibonacci() {
var a = 0, b = 1, count = 0;
for(var sum = 0; sum < 4000000;){
sum = a + b;
a = b;
b = sum;
if(sum % 2 == 0){
count += sum;
}
}
return count;
}
console.log(fibonacci());
```

Solution

With a bit of fiddling I come to this code:

```
function fibonacci() {
let s = t = 0, a = 1, b = 2;
do {
s = a + b;
a = b;
b = s;
t += s & 1 ? 0 : s;
} while (s <= 4000000);
return t;
}
console.log(fibonacci());
```

It is pretty much the same as yours with a few difference:

- I start with
`a = 1, b = 2`

as per instructions, but this means my result is 4613730 and not 4613732. `let`

will do for the variables, because they are only used in the block they are in, but since that is the same as the function`var`

is fine too.- I also follow the instructions where it says to:
*“not exceed four million”*, this includes four million. - I prefer the clean look of the
`do { ... } while`

loop. This also means I don’t have to initialized the sum. - There’s nothing wrong with your
`(sum % 2 == 0)`

check, but mine is visibly shorter. Normally I don’t care about that and would prefer yours because is easier to read.

I think the real art is to do this with less operations.