regex to match exact number of occurence of a sequence
Hello Experts,
I try to build a regex to match an exact number of occurence of a sequence/word :
For example "abc" and the number of occurence needed "3" and only three, no more no less
So :
abcXYZabcEFGabc match
abcXYZabcEFGabcKLMabc don't match because we find four time abc
abcXYZabcEFG don't match, only two is found
abcabcabc match
I have this : /^([^a]*a[^a]*){3}$/ but it work because I'm looking for "a" and not for a sequence "ab", "JPQ"
Thanks for your help!
Kinds Regards.
I try to build a regex to match an exact number of occurence of a sequence/word :
For example "abc" and the number of occurence needed "3" and only three, no more no less
So :
abcXYZabcEFGabc match
abcXYZabcEFGabcKLMabc don't match because we find four time abc
abcXYZabcEFG don't match, only two is found
abcabcabc match
I have this : /^([^a]*a[^a]*){3}$/ but it work because I'm looking for "a" and not for a sequence "ab", "JPQ"
Thanks for your help!
Kinds Regards.
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Why must it be RegExp?
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ASKER
Why a regex ? I can use it as a parameter for example.
@phr0ze and @sentner thank you I'm going to try your propositions.
@phr0ze and @sentner thank you I'm going to try your propositions.
@phr0ze
The problem with your pattern is that the *? on the bracket expression will consume any trailing "abc" strings after the first three. Simply adding the negative lookahead does not overcome this.
The problem with your pattern is that the *? on the bracket expression will consume any trailing "abc" strings after the first three. Simply adding the negative lookahead does not overcome this.
I believe the following satisfies the requirement:
^(?=(?:(?:[^a]|a[^ab])*abc){3}(?!.*?abc)).*$
ASKER
kaufmed this one don't match : affkaabcsjfjabckfsofabc
affk a abc sjfj abc kfsof abc
affk a abc sjfj abc kfsof abc
It seems it did not upon further testing. Revised:
^(?=(?:(?:[^a]|a[^b]|a(?=a))*abc){3}(?!.*?abc)).*$
Yeah, the double-a killed it. The modified version has this corrected.
ASKER
Don't match with : abffkabcsjfjabckfsofabc
ab ffk abc sjfj abc kfsof abc
ab ffk abc sjfj abc kfsof abc
ASKER CERTIFIED SOLUTION
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ASKER
@kaufmed, yes it work this time, thanks. The "problem" with this regexp is the way we build it dynamically.
The original sequence need to have three characters for example : abc
Anyway I want to thank you a lot for your time. I'm going to use an array of regex+boolean and use the logic of @sentner
I'm going to close the question
Thank you to everyone for your suggestions, have a great weekend!
The original sequence need to have three characters for example : abc
Anyway I want to thank you a lot for your time. I'm going to use an array of regex+boolean and use the logic of @sentner
I'm going to close the question
Thank you to everyone for your suggestions, have a great weekend!
ASKER
End of week, enjoy, have a nice weekend!
Thanks a lot to everyone! Have fun in your life!
Thanks a lot to everyone! Have fun in your life!
I figured I'd throw this out there just in case, but the string shouldn't be that difficult to build dynamically; granted I don't know what your environment is like. Here is a function I created to build the pattern string:
function buildPattern(src)
{
var basePattern = "^(?=(?:(?:@@@)*###){3}(?!.*?###)).*$";
var temp = "";
var t = src.charAt(0);
for (i = 1; i < src.length; i++)
{
temp += "|" + t + "[^" + src.charAt(i) + "]";
t += src.charAt(i);
}
temp = src.charAt(0) + "(?=" + src.charAt(0) + ")" + temp;
return basePattern.replace(/###/g, src).replace(/@@@/, temp);
}
Of course, make sure your source strings don't contain the sequences "###" or "@@@" :)
ASKER
Thanks a lot @kaufmed!
Sure. Glad to help!
ASKER
The language is Javascript and It sound stupid but I need to use a regexp.
Something like : /^([^a]*a[^a]*){3}$/.test(