Add two binary strings. Solved in TypeScript. https://leetcode.com/problems/add-binary

addBinary.js

// Add two binary strings directly by using a carry bit.
const addBinary = (a:string, b:string): string => {
  let result: string = '';
  let i=0;
  let carry = 0;
    
  while (i < a.length || i < b.length) {
  let a_bit = '0';
  let b_bit = '0';
  let bit = 0;
      
  if (i < a.length) {
    a_bit = a[a.length - i - 1];
  }
      
  if (i < b.length) {
    b_bit = b[b.length - i - 1];
  }
  
  const value = parseInt(a_bit) + parseInt(b_bit) + carry;
      
  if (value == 0) {
    bit = 0;
    carry = 0;
  }
  else if (value == 1) {
    bit = 1;
    carry = 0;
  }
  else if (value == 2) {
    bit = 0;
    carry = 1;
  }
  else if (value == 3) {
    bit = 1;
    carry = 1;
  }

  result = bit + result;
      
  i++;
  }
    
  result = carry ? carry + result : result;
    
  return result;
}

addBinary2.js

// Add two binary strings with helper methods to convert between binary and decimal representations.
// Then add the decimal values and convert the result back to binary.
// This is one way to implement binary addition, but there are other methods that can be done directly on the binary strings, such as using a carry bit.
const toBase10 = (s: string): number => {
  let total = 0;

  for (let i=0; i<s.length; i++) {
    const bit = parseInt(s[s.length - i - 1]);
    const val = Math.pow(2, i) * bit;
    total += val;
  }
    
  return total;
};

const toBase2 = (n: number): string => {
  let result = '';
    
  result = n.toString(2);
    
  return result;
};

function addBinary(a: string, b: string): string {
  // Convert to base10.
  const a_val = toBase10(a);
  const b_val = toBase10(b);
  const total = a_val + b_val;

  // Convert result to binary.
  return toBase2(total);
};