Question

I have an expression which matches the question mark in a url query string and I find myself needing to extend the expression to accommodate for a case where the URL I am trying to read contains the unicode equivalent of the question mark %3d

the expression is

var regexS = "[\\?&]" + name + "=([^&#]*)";

From what very little I know of RegEx I thought this might work

var regexS = "[\\?&]|[\\%3d&]" + name + "=([^&#]*)";

Thanks for the help

Answer 1

Assuming Javascript for the purposes of string escaping.

In "[\\?&]|[\\%3d&]" + name + "=([^&#]*)" note that

• concatenation (abc) has priority over alternation (a|b|c) and
• [\\%3d&] means “percent or 3 or d or ampersand” (character class).
• The escaped form of ? is %3F, not %3D. %3D means =. See wikipedia: percent encoding
• the ampersand in the first character class is present to match &q2= in www.example.com?q1=v1&q2=v2. Perhaps you want to allow escaped ampersand as well. Its escaped form is %26

You probably mean "([\\?&]|\\%3f|\\%26)" + name + "=([^&#]*)" instead.

Also note that ? has no special meaning inside a character class and doesn’t need to be escaped: "([?&]|%3f|%26)" + name + "=([^&#]*)"