javascript greatest common divisor and least common multiple

var a = 5 ;
var b = 15 ;
var min = Math.min(a,b);
var max = Math.max(a,b);
// for循环求最大公约数
for(var i = min;i>0;i--){
    if(a%i==0&&b%i==0){
        console.log(i);
        break;
    }
}


var a = 5;
var b = 15;
// for循环求最小公倍数
for(var i=max;i<=a*b;i++){
    if(i%a==0&&i%b==0){
        console.log(i)
        break;
    }
}