Regular Expressions 101

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/
style="(width:\s?\d+px;?)|(height:\s?\d+px;?)
/
g
1st Alternative
style="(width:\s?\d+px;?)
style="
matches the characters style=" literally (case sensitive)
1st Capturing Group
(width:\s?\d+px;?)
width:
matches the characters width: literally (case sensitive)
\s
matches any whitespace character (equivalent to [\r\n\t\f\v ])
? 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])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
px
matches the characters px literally (case sensitive)
;
matches the character ; with index 5910 (3B16 or 738) literally (case sensitive)
2nd Alternative
(height:\s?\d+px;?)
2nd Capturing Group
(height:\s?\d+px;?)
height:
matches the characters height: literally (case sensitive)
\s
matches any whitespace character (equivalent to [\r\n\t\f\v ])
? 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])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
px
matches the characters px literally (case sensitive)
;
matches the character ; with index 5910 (3B16 or 738) literally (case sensitive)
Global pattern flags
g modifier: global. All matches (don't return after first match)
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
g

Test String