 <p>it means 2*10^4<br> and try it in your console <code>2e4</code> the output will be <code>20000</code></p> <p>the <code>e</code> is the <a href="http://en.wikipedia.org/wiki/Scientific_notation">scientific</a> notation</p> <p>the code is equivilant to </p> <pre><code>... e.animate({along: 1}, 20000, function () { .... </code></pre>