title: Javascript array indexOf returns undefined
body: <p>When calling my function <code>checkIss()</code>, <code>issFullArray.indexOf(issToCheck)</code> always returns <code>undefined</code>.  I've run a <code>.length</code>, output the contents of <code>issFullArray</code>, I can't figure out why it's not working- the array looks fine to me.  As you can see below, I've tried explicitly setting <code>issArray</code> as an array and copying the array returned by my <code>getIssList()</code></p>
  
  <pre><code>function updateIss() {
      var issArray = [];
  
      var currService = current.u_business_service;
      var currIss = current.u_is_service;
      issArray = getIssList(currService).slice(); //getIssList() returns an arry
      if (checkIss(issArray, currIss) === false) {
          //do stuff
      }
  }
  
  function checkIss(issFullArray, issToCheck) {
      if (issFullArray.indexOf(issToCheck) &lt; 0) {
          return false;
      } else {
          return true;
      }
  }
  </code></pre>