Regular Expressions 101

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/
^\(?\d{3}\)?[\s.-]?\d{3}[\s.-]?\d{4}$
/
gm
^ asserts position at start of a line
\(
matches the character ( with index 4010 (2816 or 508) literally (case sensitive)
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
\d
matches a digit (equivalent to [0-9])
{3} matches the previous token exactly 3 times
\)
matches the character ) with index 4110 (2916 or 518) literally (case sensitive)
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
Match a single character present in the list below
[\s.-]
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
\s matches any whitespace character (equivalent to [\r\n\t\f\v \u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff])
. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
This hyphen is treated literally, which might be confusing for others. Consider escaping it or placing at the start or end of the class!
\d
matches a digit (equivalent to [0-9])
{3} matches the previous token exactly 3 times
Match a single character present in the list below
[\s.-]
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
\s matches any whitespace character (equivalent to [\r\n\t\f\v \u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff])
. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
This hyphen is treated literally, which might be confusing for others. Consider escaping it or placing at the start or end of the class!
\d
matches a digit (equivalent to [0-9])
{4} matches the previous token exactly 4 times
$ asserts position at the end of a line
Global pattern flags
g modifier: global. All matches (don't return after first match)
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
Your regular expression does not match the subject string.

Regular Expression
No Match

/
/
gm

Test String

Code Generator

Generated Code

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Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report.
For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions