261,161 questions
5469
votes
78
answers
4.9m
views
How can I validate an email address in JavaScript?
I'd like to check if the user input is an email address in JavaScript, before sending it to a server or attempting to send an email to it, to prevent the most basic mistyping. How could I achieve this?...
5468
votes
35
answers
5.5m
views
Regular expression to match a line that doesn't contain a word
I know it's possible to match a word and then reverse the matches using other tools (e.g. grep -v). However, is it possible to match lines that do not contain a specific word, e.g. hede, using a ...
4309
votes
78
answers
2.8m
views
How can I validate an email address using a regular expression?
Over the years I have slowly developed a regular expression that validates most email addresses correctly, assuming they don't use an IP address as the server part.
I use it in several PHP programs, ...
2498
votes
18
answers
1.3m
views
What is a non-capturing group in regular expressions?
How are non-capturing groups, i.e., (?:), used in regular expressions and what are they good for?
- 93.7k
2356
votes
36
answers
4.0m
views
RegEx match open tags except XHTML self-contained tags
I need to match all of these opening tags:
<p>
<a href="foo">
But not self-closing tags:
<br />
<hr class="foo" />
I came up with this and wanted to make ...
1976
votes
29
answers
1.4m
views
How do you use a variable in a regular expression?
I would like to create a String.replaceAll() method in JavaScript and think using a regex would be the most terse way to do it. However, I can't figure out how to pass a variable into a regex. I can ...
- 40.5k
1762
votes
24
answers
1.1m
views
How do you access the matched groups in a JavaScript regular expression?
I want to match a portion of a string using a regular expression and then access that parenthesized substring:
var myString = "something format_abc"; // I want "abc"
var arr = /(?:^|\s)format_(.*?...
- 548k
1389
votes
3
answers
1.4m
views
Negative matching using grep (match lines that do not contain foo) [duplicate]
How do I match all lines not matching a particular pattern using grep? I tried this:
grep '[^foo]'
- 22.3k
1352
votes
4
answers
111k
views
\d less efficient than [0-9]
I made a comment yesterday on an answer where someone had used [0123456789] in a regex rather than [0-9] or \d. I said it was probably more efficient to use a range or digit specifier than a character ...
- 55k
1216
votes
15
answers
1.6m
views
Check whether a string matches a regex in JS
I want to use JavaScript (I can also use jQuery) to do check whether a string matches the regex ^([a-z0-9]{5,})$, and get a true or false result.
match() seems to check whether part of a string ...
- 33.1k
1172
votes
10
answers
273k
views
Is there a regular expression to detect a valid regular expression?
Is it possible to detect a valid regular expression with another regular expression? If so please give example code below.
- 9,261
1092
votes
68
answers
772k
views
What is the best regular expression to check if a string is a valid URL?
How can I check if a given string is a valid URL address?
My knowledge of regular expressions is basic and doesn't allow me to choose from the hundreds of regular expressions I've already seen on the ...
- 17.8k
1060
votes
46
answers
1.2m
views
How to validate phone numbers using regex
I'm trying to put together a comprehensive regex to validate phone numbers. Ideally it would handle international formats, but it must handle US formats, including the following:
1-234-567-8901
1-234-...
1041
votes
16
answers
1.3m
views
Regular Expressions: Is there an AND operator?
Obviously, you can use the | (pipe?) to represent OR, but is there a way to represent AND as well?
Specifically, I'd like to match paragraphs of text that contain ALL of a certain phrase, but in no ...
- 36.4k
932
votes
45
answers
1.5m
views
Regex for password must contain at least eight characters, at least one number and both lower and uppercase letters and special characters
I want a regular expression to check that:
contains at least eight characters,
including at least one number and
includes both lower and uppercase letters and
include at least one special characters, ...
- 9,487