ed words are special
identifiers that are set aside by the ECMAScript specification for special use.
The specification defines three sets of reserved words. The first set is
"keywords", which are all used by the current version of the language. Here's
the full list (<a href="http://es5.github.com/#x7.6.1.1">ES5 §7.6.1.1</a>):</p>
<ul>
<li><code>break</code></li>
<li><code>case</code></li>
<li><code>catch</code></li>
<li><code>continue</code></li>
<li><code>debugger</code></li>
<li><code>default</code></li>