Sum of even numbers in an Javascript array? [duplicate]

Question

This question already has an answer here:

Getting wrong output when trying to loop through the first 50 even Fibonacci numbers in JavaScript [duplicate] (1 answer)

Closed 9 years ago.

Trying to sum the even numbers of the fibonacci sequence. Why is it not summing all of the numbers together and just using the last number? How can I sum all of the even numbers together? Here's my code:

function fibonacciSum(){
    var i;
    var fib = new Array ();

    fib[0] = 0;  
    fib[1] = 1; 
        for(i=2; i<=10; i++){  
            fib[i] = fib[i-2] + fib[i-1]; 
            var number = parseInt(fib[i]);   
            var sum = 0;  
            if (number % 2 == 0) {  
                var result = sum += fib[i];  
                }  
         }  
    console.log(result);   
}

Answer 1

You should declare sum and result outside for loop. Try this:

function fibonacciSum(){
    var i;
    var fib = new Array ();

    fib[0] = 0;  
    fib[1] = 1;
    var sum = 0; 
    var result = 0; 
    for(i=2; i<=10; i++){  
        fib[i] = fib[i-2] + fib[i-1]; 
        var number = fib[i]; 
        if (number % 2 == 0) {  
            result = sum += fib[i];  
        }  
     }  
    console.log(result);   
}

Answer 2

var sum = 0;

This is in your loop resetting the sum on every iteration. It has to be outside the loop.

Answer 3

In your solution, each run of the for loop resets "sum" with the line: var sum = 0;. Set it to 0 outside the loop.

function fibonacciSum(){
    var i;
    var fib = new Array ();
    fib[0] = 0;  
    fib[1] = 1; 
    var sum = 0;
        for(i=2; i<=10; i++){  
            fib[i] = fib[i-2] + fib[i-1]; 
                var number = parseInt(fib[i]);    
                if (number % 2 == 0) {  
                    var result = sum += fib[i];  
                }  
         }  
    console.log(result);   
}