Basic Quantifiers * + ?

Quantifiers specify how many times the preceding element should repeat.

The Three Basic Quantifiers

Quantifier	Meaning
*	Zero or more
+	One or more
?	Zero or one (optional)

Asterisk (*) - Zero or More

a* matches zero or more 'a' characters.

Notice it matches even with zero 'o's (ggle)!

Plus (+) - One or More

a+ requires at least one 'a'.

Now ggle doesn't match - we need at least one 'o'.

Question Mark (?) - Optional

a? matches zero or one 'a' - making it optional.

The 'u' is optional, so both spellings match.

Combining Quantifiers

Quantifiers with Character Sets

Practice Playground

Try:

• \d+ - match numbers
• [a-z]+ - match words
• \w+ - match word characters
• ou? - optional 'u'

Key Takeaways

• * matches zero or more (can match nothing)
• + matches one or more (requires at least one)
• ? makes the previous element optional
• Quantifiers apply to the element immediately before them
• Use with character sets: [a-z]+ matches words