Javascript Algorithm:Find All Divisors of a whole number

Problem Statement: List all divisors of a positive whole number.

e.g.

Input:

n=27

Output:

divisors=[1,3,9,27]

Solution 1( Upper bound of loop is sqrt(num) ):

let num = 27;

/*

Even numbers can have odd divisors

Odd number can't have even divisors

*/

function getAllDivisors(num) {

let result = [];

if (num == 1) {

return [1];

} else {

let max = Math.sqrt(num);

let isOdd = num % 2; //for odd number reminder 1

let i = 1;

while (i <= max) {

if (num % i == 0) {

result.push(i);

/*if is square root then it will get added twice

we want a divisor to be added once once*/

if (num / i != i) {

result.push(num/i);

}

}

if (isOdd == 1) {

i += 2;

} else {

i++;

}

}

return result;

}

}

let allDivisiors = getAllDivisors(num);

console.log(allDivisiors)

Output:

[ 1, 27, 3, 9 ]

Solution 2( Upper bound of loop is num/2 ):

let num = 27;

/*

Even numbers can have odd divisors

Odd number can't have even divisor

*/

function getAllDivisors(num) {

let result = [];

if (num == 1) {

return [1];

} else {

let max = Math.floor(num / 2);

let isOdd = num % 2; //for odd number reminder 1

let i = 1;

while (i <= max) {

if (num % i == 0) {

result.push(i);

}

if (isOdd == 1) {

i += 2;

} else {

i++;

}

}

//every number divides itself

result.push(num);

return result;

}

}

let allDivisiors = getAllDivisors(num);

console.log(allDivisiors);

Output:

[ 1, 27, 3, 9 ]