Regular Expressions 101

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/
(?<=[a-zA-Z0-9])'(?=[a-zA-Z0-9])
/
g
Positive Lookbehind
(?<=[a-zA-Z0-9])
Assert that the Regex below matches
Match a single character present in the list below
[a-zA-Z0-9]
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
' matches the character ' with index 3910 (2716 or 478) literally (case sensitive)
Positive Lookahead
(?=[a-zA-Z0-9])
Assert that the Regex below matches
Match a single character present in the list below
[a-zA-Z0-9]
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (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

Regex Debugger

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