title: Checking if at least one value in one array exists in another fails
body: <p>The below should return true, but it is reporting false:</p>
  
  <pre><code>var array1 = ['fred'];
  var array2 = ['sue', 'fred'];
  
  var modified = [];
  
  //create a new modified array that converts initials to names and vice versa 
      array1.forEach(function(element) {
              var index = array2.findIndex(el =&gt; el.startsWith(element[0]));
              if (index &gt; -1) {
                  modified.push(array2[index]);
                  array2.splice(index, 1);
              } else {
                  modified.push(element);
              }
      });
  
  console.log(modified); // should be the same as array1
  console.log(modified.some(v =&gt; array2.includes(v))); //false should be true
  </code></pre>
  
  <p>I'm trying to check if at least one value in modified exists in array2.</p>
  
  <p>the opposite is also wrong:</p>
  
  <pre><code>console.log(array2.some(v =&gt; modified.includes(v))); //false should be true
  </code></pre>
  
  <p><a href="https://jsfiddle.net/rL532z4c/" rel="nofollow noreferrer">JSFiddle</a></p>