476.js

/** ------------------------------------------------------------------------------
 * 
 * 476. Number Complement
 * Topics: Number
 * https://leetcode.com/problems/number-complement/description/
 * 
 ------------------------------------------------------------------------------ */
/**
 * @param {number} num
 * @return {number}
 */
var findComplement = function (num) {
  const toBinary = num.toString(2)

  let answer = ""
  for (const n of toBinary) {
    if (n === "0") answer += "1"
    else answer += "0"
  }

  return answer.toString(10)
}

console.log(findComplement(5))