What is the output of this code?

Question

function tobin(num) {
var res="";
while (num>0){
res=num%2+res;
num=Math.floor(num/2);
}
return res;
}
document.write(tobin(4));

output: 100. why?

Answer 1

thank you so much, Airree

Answer 2

It basically turns a decimal number to a binary number. You can run through everything:
res = num % 2 + res //4 % 2 = 0, so res = 0
num = Math.floor(num / 2) // 4 / 2 = 2, num = 2
//next iteration, num is bigger than 0
res = num % 2 + res //2 % 2 = 0, so res = 00
num = Math.floor(num / 2) //2 / 2 = 1, num is 1
//next iteration, num is bigger than 0
res = num % 2 + res //1 % 2 = 1, so res = 100
num = Math.floor(num / 2) //1 / 2 = 0.5, floor of 0.5 is 0, num = 0
//loop stops since num is 0