Regular Expressions 101

Pro

Positive Lookbehind(?<=\b(?:var|let)\s+(?:\w+(?::[^:,]*)?,\s*)*)

\ban ASCII word boundary

Non-Capturing Group(?:var|let)

1st Alternativevar

varthe literal text var (case sensitive)

2nd Alternativelet

letthe literal text let (case sensitive)

\s+any whitespace character, repeated at least once

Non-Capturing Group(?:\w+(?::[^:,]*)?,\s*)*

*repeats the group contents below any number of times:

\w+any word character, repeated at least once

Non-Capturing Group(?::[^:,]*)?

?repeats the group contents below at most once:

:the literal : (58₁₀ / 72₈ / 3A₁₆)

Negated Character Class[^:,]*

*matches any number of characters outside the set below:

:the literal : (58₁₀ / 72₈ / 3A₁₆)

,the literal , (44₁₀ / 54₈ / 2C₁₆)

\s*any whitespace character, repeated any number of times

\w+any word character, repeated at least once

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

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26 tokens

(?<=\b(?:var|let)\s+(?:\w+(?::[^:,]*)?,\s*)*)\w+

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