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A Simple Regular Expression Question - Why Doesn't This Match?


doug
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This truly is a simple regular expression question. :)I have a variable theTitle with the value: "Test Group A BTYZ311-1"And a variable courseCode with the value "BTYZ311".I want to see if theTitle contains courseCode followed by a dash followed by 1 or more digits.This is my test:

var matchExp = new RegExp(courseCode + '\-\d+', "i");if (!matchExp.test(theTitle)) {   // do something because theTitle doesn't seem to contain the courseCode plus dash + number}

The problem is the .test() method always returns false, so there must be something wrong with my RegExp.Does anybody happen to see what that might be?Thanks,doug

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Alerting matchExp reveals the problem, and it's one of the reasons I never use the RegExp constructor. It's just counter-intuitive. Everything is fine except for your escape character, which needs to be escaped twice. So \\d+I think in this context that escaping the - character is not necessary. At least, it works for me in FF without being escaped.

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Alerting matchExp reveals the problem, and it's one of the reasons I never use the RegExp constructor. It's just counter-intuitive. Everything is fine except for your escape character, which needs to be escaped twice. So \\d+I think in this context that escaping the - character is not necessary. At least, it works for me in FF without being escaped.
Thanks. That did work! I sort of see why and also don't see why. I thought that RegExp was supposed to take a string and turn it into a regular expression. \d only has one interpretation in a regular expression - a digit. So I thought that was ok as is. In fact, I would have guessed that \\d+ meant "find a backslash, the letter d and a plus sign."But anyway, I'll just try to remember to escape all my backslashes in RegExp from now on.You are right, of course, about \-, but I tend to escape all my punctuation so I don't have to remember which has special meaning and which doesn't.Thanks!doug Edited by doug Lerner
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