title: jQuery add to current width
body: <p>I need this code to, if <code>#vid</code> is present, add 855px to its current width. If not, it should do nothing. I'm not sure how to get jQuery to add to an already existing number, but I'm sure it's pretty simple. Here is the code I have so far:</p>
  
  <pre><code>if ($("#vid").length) {
              $("#img-container").width(+=855),
          } else {
              return false;
          }
  });
  </code></pre>