需要帮助编写代码以将十进制转换为二进制而不使用 toString

Question

I'm trying to create my own decimal to binary converter with the method of decrementing the inputted variable (decimal value), by dividing it by 2 and storing the remainder (like 2nd grade math remainder), which is always either 0 or 1. Each of the remainder values i thin should be stored in an array and I think maybe put in backwards so that the most significant digit is first in the array (this is because when decrementing the remainer values are filled in left to right). Soooo yea i dont really know how to store the remainder values in an array using a function Thanks in advance and if something is confusing then feel free to ask because im not even sure if this is the best method of doing this its just what i came up with

function decimalToBinary(num) {
  var bin = 0;
  while (num > 0) {
  bin = num % 2 + bin;
  num >>= 1; // basically /= 2 without remainder if any
  }
  alert("That decimal in binary is " + bin);
}

Answer 1

Your code is almost correct. The main problem is that bin starts out as 0 ; when you add a digit, they are added numerically, so your code ends up just counting the binary 1 s: in this manner, 10 is initial 0 , and +1+0+1+0 , resulting in 2 . You want to handle it as a string: ""+1+0+1+0 results in 1010 . So, the only needed change is:

var bin = "";

If you want to solve it using arrays, with minimal changes to your code, it would be:

function decimalToBinary(num) {
  var bin = [];
  while (num > 0) {
  bin.unshift(num % 2);
  num >>= 1; // basically /= 2 without remainder if any
  }
  alert("That decimal in binary is " + bin.join(''));
}

Here, I use .unshift to add an element to the head of the array (and renumbering the remaining elements); .join() to collect them all into a string.

Or this:

function decimalToBinary(num) {
  var bin = [];
  while (num > 0) {
  bin[bin.length] = num % 2;
  num >>= 1; // basically /= 2 without remainder if any
  }
  alert("That decimal in binary is " + bin.reverse().join(''));
}

This is not as good, but illustrates some more things you can do with arrays: taking their length, setting an arbitrary element, and flipping them around.

Answer 2

I have written a custom Decimal to Binary method:

function toBinary (input) {
  let options = [1];
  let max = 0;
  let i = 1;

  while(i) {
    max = Math.pow(2, i);
    if (max > input) break;

    options.push(max);
    i++;
  }

  let j = options.length;
  let result = new Array(j);
  result.fill("0");
  while(j >= 0) {
    if (options[j] <= input) {
      result[j] = "1"
      input = input - options[j];
    }
    j--;
  }
  return [...result].reverse().join("");
}




//Test the toBin method with built-in toString(2)

toBinary(100) === (100).toString(2) // true
toBinary(1) === (1).toString(2)     // true
toBinary(128) === (128).toString(2) // true