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Module 2 · Les 2 van 46/32 in de cursus~10 min
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Exacte hoeveelheden `{n,m}`

When you need precise control over the number of repetitions, you use the brace notation {n,m}:

SyntaxMeaning
\d{4}Exactly 4 digits
\d{2,4}From 2 to 4 digits
\d{3,}At least 3 digits

{n} is equivalent to {n,n}. {n,} has no maximum. {,m} is not supported in JavaScript (you must write {0,m}).

Code
Pattern: \d{4}
Sample:  Anni: 2020, 2024, 1999, errore 99.
               ^^^^  ^^^^  ^^^^

{4} stops the match at exactly four digits: 99 does not match because it has only two. 12345 would match the first four digits (1234), not the whole number.

Open intervals and repetition limits

The curly brace notation is flexible: {n} indicates exact repetition, {n,m} a closed range from n to m, while {n,} leaves the upper limit open ("at least n times"). The engine processes these efficiently, reducing the ambiguities of generic quantifiers.

Try it

Oefening#regex.m2.l2.e1
Pogingen: 0Laden…

Find every 4-digit year in the text (e.g. `2024`, but not `99`).

Editor laden…
Toon hint

Exactly 4 digits: use the {4} notation on the \\d class.

Oplossing beschikbaar na 3 pogingen

Review exercise

Oefening#regex.m2.l2.e2
Pogingen: 0Laden…

Find every number made of 2, 3 or 4 digits (excluding 1-digit numbers and numbers 5+ digits long).

Editor laden…
Toon hint

Range {2,4}: minimum 2, maximum 4 digits. Without anchors it will also match the first 4 digits of 12345.

Oplossing beschikbaar na 3 pogingen

Additional challenge

Oefening#regex.m2.l2.e3
Pogingen: 0Laden…

Find phone numbers in the format `XXX-XXXX` (exactly 3 digits, dash, exactly 4 digits).

Editor laden…
Toon hint

Use curly braces {3} and {4} applied to the \d class.

Oplossing beschikbaar na 3 pogingen