Q:

Why does jslint complain when I escape the < character in a RegEx? 

The code: var foo = /\</;
When I go to jslint.com and enter that in, I get:
Problem at line 1 character 12: Unexpected '\'. 
It used to tell me Unexpected escaped character '<' in regular expression.  but times have changed. 
So I'm just curious, why?  If you try var foo = /\>/; it doesn't care, what's the deal with <? 

A:

If you have a two simple divs, the difference is clear:
<div> < </div> <! --Missing right angle bracket, bad markup-->
<div> > </div> <! --No problem, just a greater than text node-->

JSLint does not assume that the script is a standalone file or inside a script tag of an HTML document.  In markup languages such as XUL, MXML, XAML, TVML, LZX, XHTML5 or SVG, the script tag content is treated like the first div in the above example, so the left angle bracket will look like the start of a tag.  In those languages, use an entity replacement or a CDATA block to wrap the left angle bracket and ampersand characters:
<script> 
if ( -1 &lt; 0 &amp;&amp; true ! == false) {} 
</script>

<script>
<![ CDATA[
if ( -2 < 0 && true ! == false) {}
]]>
</script>

References

Escaped Markup Considered Harmful

