Regular Expressions 101

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/
dialog(?! box)
/
gm
dialog
matches the characters dialog literally (case sensitive)
Negative Lookahead
(?! box)
Assert that the Regex below does not match
box
matches the characters box literally (case sensitive)
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.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
gm

Test String

Regex Debugger

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