Algorithms in Javascript: CTCI 1.5 One Away: Given 2 strings, determine if they differ from each other by a single character, either via insertion, deletion or replacement of a character.

ctci-1.5-does-differ-by-one.js

const isDifferByOne = (s1, s2) => {
  if(s1.length > s2.length + 1 || 
     s2.length > s1.length + 1) {
    return false;
  }
  
  let count = 0;
  let charMap = new Map();
  let a1 = s1.split('');
  let a2 = s2.split('');
  const len = a1.length > a2.length ? a1.length : a2.length; 
  for(let i=0; i < len; i++){
    charMap.set(s1[i], 1);
    let whichIndex = a2.indexOf(s1[i]);
    if(whichIndex >=0) {
      charMap.delete(s1[i]);
      a1.splice(whichIndex, 1);
      a2.splice(whichIndex, 1);
    } else {
      charMap.set(s2[i], 1);
      count++;
    }
  }
  return count === 1;
}

let a = 'abbc', 
    b = 'abbcd';
console.log(isDifferByOne(a, b));