Javascript Complex RegEx with variables

Question

I am using this tool to build a regex http://www.gethifi.com/tools/regex

I found that the one below works for me if, for example, I am looking to match $aazz[AB]:

var regex = /[\+\=\-\*\^\\]\$aazz\[AB\]/g;

I have read the other posts on the RegEx constructor in Javascript but cannot manage to make the following work:

var preToken = "[\+\=\-\*\^\\]";    
var toFind = "\$aazz\[AB\]";

var stringToReplace = "/" + preToken + toFind + "/";

var regex = new RegExp(stringToReplace, "g");

Here is the jsbin http://jsbin.com/ifeday/3/edit

Thanks

pimvdb · Accepted Answer · 2012-08-17 15:38:26Z

4

When creating regular expressions from strings, you need to escape your backslashes twice.

\ becomes \\
\\ becomes \\\\

So, you can try (in a character class not everything needs escaping):

var preToken = "[+=\\-*^\\\\]"; 
var toFind = "azz\\[A\\]";

Also, the string source for your regular expression does not need to be bound by /s, but I see in your jsBin that you've already corrected that.

Update your jsBin with these variable declarations, it should work now.

edited Aug 17, 2012 at 15:38

pimvdb

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answered Aug 17, 2012 at 15:33

jackwanders

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