How To Sum Numbers Saved As Array In Javascript With While Loop

Where is the mistake? I want to sum every number in the array. The alert says NaN. var numbers = [10, 42, 5, 87, 61, 34, 99]; var i = 0; var e = 0; while(i <= numbers.length) {

Solution 1:

This line is the reason:

while(i <= numbers.length) {

Arrays are 0 index so you can go from index 0 (inclusive) until numbers.length (exclusive). You are going beyond that limit, causing you to access an element that isn't defined at the given index. You must do this instead:

while(i < numbers.length) {

Solution 2:

Alternatively using the ES2015 syntax you can do it like this.

let numbers = [10, 42, 5, 87, 61, 34, 99];
let sum = numbers.reduce((a,b) => a + b);

You can read about Array.prototype.reduce(accumulator, element, callback, startingValue)here.

Solution 3:

Your condition is wrong, just use < insteead of <=

while(i < numbers.length) 

Solution 4:

There's a few ways you can improve this. The first is that you want to change your condition to i < numbers.length, not i <= numbers.length. As you've written it, the last number will never be counted.

Another way you can improve this is using the += notation -- there's no need to write e = e + numbers[i] when you can write e += numbers[i].

Solution 5:

You could íterate from the end of the array with a post increment and a check for truthyness in the while condition.

Inside just add the item.

var numbers = [10, 42, 5, 87, 61, 34, 99],
    i = numbers.length,
    e = 0;

while (i--) {
    e += numbers[i]; 
}

console.log(e);