Say you have this regex, that checks if a string has one digit in it, and nothing else:

/^\d$/

You can use the ? quantifier to make it optional, thus requiring zero or one:

/^\d?$/

but what if you want to match multiple digits?

You can do it in four ways, using +, *, {n}, and {n,m}.

+

Match one or more (>=1) items

/^\d+$/

/^\d+$/.test('12')     //✅
/^\d+$/.test('14')     //✅
/^\d+$/.test('144343') //✅
/^\d+$/.test('')       //❌
/^\d+$/.test('1a')     //❌

*

Match 0 or more (>= 0) items

/^\d*$/

/^\d*$/.test('12')     //✅
/^\d*$/.test('14')     //✅
/^\d*$/.test('144343') //✅
/^\d*$/.test('')       //✅
/^\d*$/.test('1a')     //❌

{n}

Match exactly n items

/^\d{3}$/

/^\d{3}$/.test('123')  //✅
/^\d{3}$/.test('12')   //❌
/^\d{3}$/.test('1234') //❌

/^[A-Za-z0-9]{3}$/.test('Abc') //✅

{n,m}

Match between n and m times:

/^\d{3,5}$/

/^\d{3,5}$/.test('123')    //✅
/^\d{3,5}$/.test('1234')   //✅
/^\d{3,5}$/.test('12345')  //✅
/^\d{3,5}$/.test('123456') //❌

m can be omitted for an open-ended range meaning at least n items:

/^\d{3,}$/

/^\d{3,}$/.test('12')        //❌
/^\d{3,}$/.test('123')       //✅
/^\d{3,}$/.test('12345')     //✅
/^\d{3,}$/.test('123456789') //✅

Lessons in this unit:

0:	Introduction
1:	Introduction
2:	Anchoring
3:	Match Items in Ranges
4:	Matching a Range Item Multiple Times
5:	Negating a Pattern
6:	Meta Characters
7:	Regular Expressions Choices
8:	▶︎ Quantifiers
9:	Optional Items
10:	Groups
11:	Capturing Groups
12:	Using match and exec Without Groups
13:	Noncapturing Groups
14:	Flags
15:	Inspecting a Regex
16:	Escaping
17:	String Boundaries
18:	Replacing
19:	Greediness
20:	Lookaheads
21:	Lookbehinds
22:	Unicode
23:	Unicode Property Escapes
24:	Examples