Will this be optimal?

function kangaroo(x1, v1, x2, v2) {
        var difference=0;

       var calculate=function(){
           if((x1<x2)&&((v1<v2)||(v1==v2))){
         return "NO"
     }
           else{
while(Math.sign(difference)!=-1){
    x1+=v1;
    x2+=v2;
    difference=x2-x1;
    if(difference==0){
        return "YES"
    }
}
        return "NO"
           }
       }();
    return calculate;
}

Check the difference between the two kangaroos on each jump if they come to become 0 then yes or no if the difference goes to negative-This is the main logic other anomaly(Infinite looping problem) is if both distances are equal from start theyll never produce negative or 0 so print no and see if the second kangaroo is way ahead than the first one from start if yes then print "No"