function smallestCommons(arr) {
arr=arr.sort(function(a,b){
  return a>b;
});

let myarr=[],newarr;
for(let i=1;i<9999999999;i++){
  let num=arr[1]*i;
  if(num%arr[0]===0){
    for(let j=arr[0]+1;j<arr[1];j++){
      if(num%j==0){
        myarr.push(j);
    }

    }
    if(myarr.length!==arr[1]-arr[0]-1){
      myarr.splice(0,myarr.length);
    }else{return num;}
  }
}
}

console.log(smallestCommons([1,5]));

function lcm(a, b) {
    // First, find the greatest common factor
    let gcf = 1;
    let r1 = a;
    let r2 = b;
    while (r1 !== r2) {
        let diff = Math.abs(r1 - r2);
        r1 = Math.min(r1, r2);
        r2 = diff;
    }
    gcf = r1;

    // Divide the product of a and b with the GCF:
    return (a * b) / gcf;
}