## The problem

This is problem 2 from the Project Euler.

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 that do not exceed the nth term, find the sum of the even-valued terms.

## Let's begin

Initialise variables and common functions:

```
var test_values = [10, 18, 23, 43]; // list of numbers we wanna test
// this function execute the code and records the time to execute
function run_function(func, test_values) {
for(var i in test_values){
console.log('Test value:', test_values[i]);
var t0 = performance.now();
console.log('Output:', func(test_values[i]));
var t1 = performance.now();
console.log("Took " + (t1 - t0) + " milliseconds.");
console.log();
}
}
```

## Attempt #1: recursive functions

The recursive way...

```
function fiboEvenSum(n) {
var fib_nums = [1, 2];
fib_nums = add(n, fib_nums);
var sum = 0;
for(var i in fib_nums){
if(fib_nums[i]%2===0){
sum = sum + fib_nums[i]
}
}
return sum;
}
function add(n, fib_nums){
var c = fib_nums[fib_nums.length-1] + fib_nums[fib_nums.length-2];
fib_nums.push(c);
if(fib_nums.length<n){
return add(n, fib_nums);
}else{
return fib_nums;
}
}
run_function(fiboEvenSum, test_values);
```

The output:

```
Test value: 10
Output: 44
Took 0.13000000035390258 milliseconds.
Test value: 18
Output: 3382
Took 0.05999999848427251 milliseconds.
Test value: 23
Output: 60696
Took 0.1049999991664663 milliseconds.
Test value: 43
Output: 350704366
Took 0.08000000525498763 milliseconds.
```

Here's my solution, can it be any better?

This is my Project Euler Challenge journey; anyone wants to do this together? It will be fun and we can learn a thing or two by solving this problem in different ways.

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