Question

I came across one article by john resig explaining JavaScript Inheritance.
http://ejohn.org/blog/simple-javascript-inheritance/

In this post there is a Class implementation code where the starting line has a regexp

fnTest = /xyz/.test(function(){xyz;}) ? /\b_super\b/ : /.*/;

Can any one tell me what is the meaning of this?

Answer 1

The fnTest is used to check whether a method uses _super somewhere. To do that, the function is implicitly converted to a string (toString) and tested against the regular expression (in // Copy the properties over onto the new prototype).

However, not all implementations really yield the source code of a function when it’s toString method is called. So this test checks whether the function(){xyz;} can be tested against containing xyz – if not, the always-matching /.*/ is used instead of /\b_super\b/.