Is it okay to use with()?
<p>Once, I saw an example like this:</p>

<pre><code>var a, x, y;
var r = 10;
with (Math) {
  a = PI * r * r;
  x = r * cos(PI);
  y = r * sin(PI / 2);
}
</code></pre>

<p>And it looks very convenience, because that way I don't have to type all the <code>Math.</code>s.</p>

<p>But when I take a look at the <a href="https://developer.mozilla.org/en/JavaScript/Reference/Statements/with#Description" rel="nofollow">MDN</a>, it says:</p>

<blockquote>
  <p>Using <code>with</code> is not recommended, and is <em>forbidden in ECMAScript 5 strict mode</em>. The recommended alternative is to assign the object whose properties you want to access to a temporary variable.</p>
</blockquote>

<p>So is it okay to use <code>with()</code>? In <code>HTML5</code>?</p>
