Hacker Rank Challenge: https://www.hackerrank.com/challenges/between-two-sets/problem?isFullScreen=true

getTotalX.js

function getTotalX(a, b) {
    // Write your code here
    let lowerBoundInt = a[a.length - 1];
    let upperBoundInt = b[0];
    let arrayInt = [];
    let arrayForFactorsOfA = [];
    let arrayWhoseFactorsAreB = [];
    let finalArr = [];
    
    if(lowerBoundInt > upperBoundInt) {
        return 0;
    }
    
    for(let i=lowerBoundInt; i<= upperBoundInt; i++) {
        arrayInt.push(i);
    }
    
    arrayInt.forEach(item => {
        let count = 0
        a.forEach((element, i) => {
            (item % element === 0) && count++;
            (count === a.length) && arrayForFactorsOfA.push(item);
        })
    });
    
    arrayInt.forEach(item => {
        let count = 0
        b.forEach((element, i) => {
            (element % item === 0) && count++;
            (count === b.length) && arrayWhoseFactorsAreB.push(item);
        })
    });
    
    //finds the items that exist in both arrays
    
    finalArr = arrayWhoseFactorsAreB.filter(item => arrayForFactorsOfA.includes(item))
    
    return finalArr.length;
}