title: Compare two string and count letters that are different
body: <p>I have to write a function that takes in two strings and compares them then returns the number of letters in the strings that are different. For example "ABC" and "DEC" should return 4. My function always turns up one short because of how I am comparing them. I've looked but can't seem to find a fix. </p>
  
  <p>I have tried looping through the string without splitting and ended up with the same problem.</p>
  
  <pre><code>function makeAnagram(a, b) {
      let result = 0;
  
      let a1 = a.split("").sort();
      let b1 = b.split("").sort();
      for(let i = 0; i &lt; b1.length; i++){
          if(a1.indexOf(b1[i] &lt; 0)){
              result += 1;
          }
      }
  
  
      return result;
   }
  </code></pre>