Regular Expressions 101

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/
\d(?=.*\d(?:\s*\d){3}\s*$)
/
gm
\d matches a digit (equivalent to [0-9])
Positive Lookahead
(?=.*\d(?:\s*\d){3}\s*$)
Assert that the Regex below matches
.
matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\d matches a digit (equivalent to [0-9])
Non-capturing group
(?:\s*\d){3}
{3} matches the previous token exactly 3 times
\s
matches any whitespace character (equivalent to [\r\n\t\f\v \u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\d matches a digit (equivalent to [0-9])
\s
matches any whitespace character (equivalent to [\r\n\t\f\v \u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
$ 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

Substitution

Processing...