How do I convert an integer to binary in JavaScript?

Question

I’d like to see integers, positive or negative, in binary.

Rather like this question, but for JavaScript.

Answer 1

function dec2bin(dec){
    return (dec >>> 0).toString(2);
}

dec2bin(1);    // 1
dec2bin(-1);   // 11111111111111111111111111111111
dec2bin(256);  // 100000000
dec2bin(-256); // 11111111111111111111111100000000

---

You can use Number.toString(2) function, but it has some problems when representing negative numbers. For example, (-1).toString(2) output is "-1".

To fix this issue, you can use the unsigned right shift bitwise operator (>>>) to coerce your number to an unsigned integer.

If you run (-1 >>> 0).toString(2) you will shift your number 0 bits to the right, which doesn't change the number itself but it will be represented as an unsigned integer. The code above will output "11111111111111111111111111111111" correctly.

This question has further explanation.

-3 >>> 0 (right logical shift) coerces its arguments to unsigned integers, which is why you get the 32-bit two's complement representation of -3.