JScript Regex XML attribute using Sub-Match?

Question

I have the following text I'm searching:

<add key="Directory" value="" />

And this is my regex:

add key=\x22Directory\x22 value=\x22([^\x22]*)\x22

My desired output is:

<add key="Directory" value="blue" />

But, with what I have, it seems to be selecting the whole tag and producing:

<blue />

But, according to regex101, it shouldn't be. What am I doing wrong?

I have also tried:

value=\x22([^\x22]*)\x22

But, that returns:

<add key="Directory" blue />

Regex101 is telling me the following. It matches and notices the first capturing group but yet is still replacing the entire value=""

regex submatch

The "producing" part of your post isn't currently showing up so it's hard to know what you're asking. — Colin
– Colin, Commented Mar 4, 2015 at 22:43
Don't use RegEx to parse XML. Use the DOM and XPath/CSS selectors if possible or another XML Api if needed. — ThW
– ThW, Commented Mar 5, 2015 at 9:47
@ThW, I agree but sadly I am writing a batch file and this is the best thing I found. jrepl. — Kyle
– Kyle, Commented Mar 5, 2015 at 17:30

Colin · Accepted Answer · 2015-03-04 23:31:59Z

1

You want to use lookaround. So something like this, where the spot you're trying to pinpoint is preceded and proceeded by the lookaround text:

(?<=<add key="Directory" value=")[^"]*(?=" />)

Tweak to your liking, but that's the basic idea.

EDIT:

Since using jscript, try something like this (tweaking the substitution):

var re = /add key=\x22Directory\x22 value=\x22([^\x22]*)\x22/; 
var str = '<add key="Directory" value="" />'; //<- sample input. it could be your whole XML doc.
var subst = 'add key="Directory" value="Blue"'; 

var result = str.replace(re, subst);

or...

var re = /(add key=\x22Directory\x22 value=\x22)[^\x22]*(\x22)/; 
var str = '<root>\n    <someOtherElement/>\n    <add key="Directory" value="" />\n</root>';
var subst = '$1Blue$2'; 

var result = str.replace(re, subst);

edited Mar 4, 2015 at 23:31

answered Mar 4, 2015 at 22:55

Colin

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5 Comments

Kyle Over a year ago

Hmm that seems to result in a syntax error in regular expression: i.imgur.com/JnQRQgA.png

Colin Over a year ago

Your test tool may not support lookbehind. What technology will you ultimately be running the expression in? .NET will work fine. FWIW - The verbatim expression ran great in Expresso, which is what I use for testing.

Kyle Over a year ago

I will be using JScript (jrepl specifically) if that helps in anyway. I've been testing with regex101 which also complained of syntax errors. I was able to fix the syntax errors by removing the < you had in the first lookaround.But, it also didn't work

Colin Over a year ago

Edited my answer. If you use your original expression that matches the whole thing, you can just have the substitution include the original value + your added attribute value.

Colin Over a year ago

I also included a second option where you invert what you capture, then perform the substation on what's in-between via: '$1Blue$2' where $1 is the first group you capture in parenthesis "Blue" is the value you want to stick in-between and $2 is the second group you capture via the modified expression (whose parenthesis have changed since the original expression like "(add key=\x22Directory\x22 value=\x22)[^\x22]*(\x22)").

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