Guys please help me explain the output of these while loop code.

Question

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

Answer 1

The function "brown(4)" is called inside the document.write so that makes num equivalent to 4, the variable red is declared as an empty string and then since 4 is more than 0 the while loop is entered.

"red = num % 2 + red" means red = 4 % 2 + " ", 4 % 2 is 0 and 0 + " " is "0" (as a string since red was declared as a string), num is halved so is now 2 and since 2 is more than 0 the loop continues...

"red = num % 2 + red" is now red = 2 % 2 + '0', 2 % 2 is 0 and 0 + '0' is "00", num is again halved so is now 1 and 1 is more than 0 so the loop still continues...

"red = num % 2 + red" is now red = 1 % 2 + '00', 1 % 2 is 1 and 1 + '00' is "100", num is once again halved to 0.5 and this time Math.floor takes effect since that is a decimal and makes num 0, 0 is not more than 0 so the loop is exited and the value of red is return in place of the "brown(4)" and the value of red ("100") is written to the screen.

Edit: No Problem :)

Answer 2

Thanks a lot, you made it so clear to my understanding.