title: Older browser compatibility for my web application(JS) ES5
body: <p>Older browser compatibility for my web application.
  I need to create a web application (HTML5 &amp; JS (ES5)) that works on Mozilla Firefox 14, my operating system is mac os 10.6
  My question is : does jquery work on this browser ?
  I have a lot of problems on compatibility like :</p>
  <p>Example of code that doesn't work:</p>
  <p><code>&quot;SyntaxError: invalid for/in left-hand side&quot;</code></p>
  <pre class="lang-js prettyprint-override"><code>var query = &quot;&quot;;
  if(params &amp;&amp; !(flags &amp; AJAX_JSON)) {
      for(const p in params) {
          if(query.length)
              query += &quot;&amp;&quot;;
          query += encodeURIComponent(p);
          query += &quot;=&quot;;
          query += encodeURIComponent(params[p]);
      }
  }
  </code></pre>