Trying to find factors of a number in JS

Question

I am just starting JS, and understand the concept of finding a factor. However, this snippet of code is what I have so far. I have the str variable that outputs nothing but the first factor which is 2. I am trying to add each (int) to the str as a list of factors. What's the wrong in below code snippet?

function calculate(num) {
    var str = "";
    var int = 2;
    if (num % int == 0) {
        str = str + int;
        int++;
    } else {
        int++;
    }
    alert(str);
}

calculate(232);

Answer 1

UPDATED ES6 version:

As @gengns suggested in the comments a simpler way to generate the array would be to use the spread operator and the keys method:

const factors = number => [...Array(number + 1).keys()].filter(i=>number % i === 0);
console.log(factors(36));      //  [1, 2, 3, 4, 6, 9, 12, 18, 36]

ES6 version:

const factors = number => Array
    .from(Array(number + 1), (_, i) => i)
    .filter(i => number % i === 0)

console.log(factors(36));      //  [1, 2, 3, 4, 6, 9, 12, 18, 36]

https://jsfiddle.net/1bkpq17b/

• Array(number) creates an empty array of [number] places

• Array.from(arr, (_, i) => i) populates the empty array with values according to position [0,1,2,3,4,5,6,7,8,9]

• .filter(i => ...) filters the populated [0,1,2,3,4,5] array to the elements which satisfy the condition of number % i === 0 which leaves only the numbers that are the factors of the original number.

Note that you can go just until Math.floor(number/2) for efficiency purposes if you deal with big numbers (or small).