JavaScript Regex Examples

1/* 
2
3CHEATSHEET
4
5. — (period) Matches any single character, except for line breaks.
6* — Matches the preceding expression 0 or more times.
7+ — Matches the preceding expression 1 or more times.
8? — Preceding expression is optional (Matches 0 or 1 times).
9^ — Matches the beginning of the string.
10$ — Matches the end of the string. 
11
12\d OR [0-9] — Matches any single digit character.
13\w OR [A-Za-z0-9_] — Matches any word character (alphanumeric & underscore).
14[XYZ] — Character Set: Matches any single character from the character within the brackets. You can also do a range such as [A-Z]
15[XYZ]+ — Matches one or more of any of the characters in the set.
16[^A-Z] — Inside a character set, the ^ is used for negation. In this example, match anything that is NOT an uppercase letter.
17
18g — Global search
19i — case insensitive search
20
21(x) — Capturing Parenthesis: Matches x and remembers it so we can use it later.
22(?:x) — Non-capturing Parenthesis: Matches x and does not remembers it.
23x(?=y) — Lookahead: Matches x only if it is followed by y.
24*/
25
26// Replace word starting at: 
27/\b(\w*surveys_questions_key\w*)\b/
28
29// Extract all image urls
30  var urlRegex = new RegExp(/(https?:\/\/www.coderecipes.org).([a-z\.]{2,6})([\/\w\.-]*)*\/?\S/g);
31
32// Unix Path
33const regex = /((?:\/[\w\.\-]+)+)([a-z])/i;
34const extraction = regex.exec(unixPath);
35
36/* String  Replace http* with an HTML anchor
37(http\S+) is a capturing group which captures 'http' followed by 1 or more non-whitespace characters (\S is a non-whitespace character)
38*/
39const anchorified = value.replace(/(http\S+)/gi, '<a href="$1"> $1 </a>');
40
41// Anything within parenthesis
42const regexAnythingWithinParenthesis = \(([^\)]+)\)
43
44// Has string
45const regexHasPort = /port/;
46const regexHasPortViaConstructor = new RegExp('port', 'i');
47const result = regexHasPort.test('port number is 9095'); //true
48
49// Has numbers only
50const regexOnlyNumbers = /\d/;
51const result = regexOnlyNumbers.test('foo bar'); //false
52const result1 = regexOnlyNumbers.test('12'); //true
53
54// Has 4 numbers with dashes in exact sequence
55const regexOnly4NumbersWithDashes = /\d-\d-\d-\d/;
56const result = regexOnly4NumbersWithDashes.test('1-2-3-4'); //true
57const result1 = regexOnly4NumbersWithDashes.test('1-x-3-4'); //false
58const result2 = regexOnly4NumbersWithDashes.test('1-3-4'); //false
59
60// Has n numbers separated with dashes
61const regexOnlyNumbersWithDashes = /\d+-\d+/;
62const result = regexOnlyNumbersWithDashes.test('1-2-3-4'); //true
63const result1 = regexOnlyNumbersWithDashes.test('12222222-222222'); //true
64const result2 = regexOnlyNumbersWithDashes.test('foo-bar'); //false
65
66// Name Identifier (match: 'pod' once, numbers 1+ times, 'id' once) 
67const regexNameIdentifier = /pod(\d)+id/;
68const result = regexNameIdentifier.test('pod1223id'); //true
69const result = regexNameIdentifier.test('pod1223i'); //false
70const result = regexNameIdentifier.test('podXXid'); //false
71
72// Name Identifier (optional: 'pod' once, any number)
73const regexNameIdentifierOptional = /(pod)?(\d)+/i;
74const result = regexNameIdentifierOptional.test('pod122333'); //true
75const result = regexNameIdentifierOptional.test('rc122333'); //true
76const result = regexNameIdentifierOptional.test('rcXXX'); //false
77
78// Capital Letters
79const regexCapitalLetters = /[A-Z]/g;
80const result = regexCapitalLetters.test('AAs');
81
82// Capture Data and Use it Later
83const regexCapture = /([A-Z])/;
84
85
86// removeCamelCase Function
87function removeCamelCase(str){
88  //Replace each capital Letter with a space and that Letter
89  const addSpaces = str.replace(/([A-Z])/g, ' $1');  
90  const transformToLowerCase = addSpaces.replace(/([A-Z])/g, c => c.toLowerCase());
91  const upperFirstLetter = transformToLowerCase.replace(/^[a-z]/, c => c.toUpperCase());
92  const addDot = upperFirstLetter.replace(/(\w)$/, '$1.');
93  return addDot;
94}
95const result = removeCamelCase('myFunction');
96
97// Split string keeping the delimiter
98const splitByHttp = value.split(/(?=http)/);
99
100// Test World Country Codes
101const regex = /^(AF|AX|AL|DZ|AS|AD|AO|AI|AQ|AG|AR|AM|AW|AU|AT|AZ|BS|BH|BD|BB|BY|BE|BZ|BJ|BM|BT|BO|BQ|BA|BW|BV|BR|IO|BN|BG|BF|BI|KH|CM|CA|CV|KY|CF|TD|CL|CN|CX|CC|CO|KM|CG|CD|CK|CR|CI|HR|CU|CW|CY|CZ|DK|DJ|DM|DO|EC|EG|SV|GQ|ER|EE|ET|FK|FO|FJ|FI|FR|GF|PF|TF|GA|GM|GE|DE|GH|GI|GR|GL|GD|GP|GU|GT|GG|GN|GW|GY|HT|HM|VA|HN|HK|HU|IS|IN|ID|IR|IQ|IE|IM|IL|IT|JM|JP|JE|JO|KZ|KE|KI|KP|KR|KW|KG|LA|LV|LB|LS|LR|LY|LI|LT|LU|MO|MK|MG|MW|MY|MV|ML|MT|MH|MQ|MR|MU|YT|MX|FM|MD|MC|MN|ME|MS|MA|MZ|MM|NA|NR|NP|NL|NC|NZ|NI|NE|NG|NU|NF|MP|NO|OM|PK|PW|PS|PA|PG|PY|PE|PH|PN|PL|PT|PR|QA|RE|RO|RU|RW|BL|SH|KN|LC|MF|PM|VC|WS|SM|ST|SA|SN|RS|SC|SL|SG|SX|SK|SI|SB|SO|ZA|GS|SS|ES|LK|SD|SR|SJ|SZ|SE|CH|SY|TW|TJ|TZ|TH|TL|TG|TK|TO|TT|TN|TR|TM|TC|TV|UG|UA|AE|GB|US|UM|UY|UZ|VU|VE|VN|VG|VI|WF|EH|YE|ZM|ZW)$/;
102const portugal = regex.test('PT'));
103const rdm = regex.test('XX'));
104
105// Test European VAT Codes
106const regexEuropeanVATCodes = /^((AT)?U[0-9]{8}|(BE)?0[0-9]{9}|(BG)?[0-9]{9,10}|(CY)?[0-9]{8}L|(CZ)?[0-9]{8,10}|(DE)?[0-9]{9}|(DK)?[0-9]{8}|(EE)?[0-9]{9}|(EL|GR)?[0-9]{9}|(ES)?[0-9A-Z][0-9]{7}[0-9A-Z]|(FI)?[0-9]{8}|(FR)?[0-9A-Z]{2}[0-9]{9}|(GB)?([0-9]{9}([0-9]{3})?|[A-Z]{2}[0-9]{3})|(HU)?[0-9]{8}|(IE)?[0-9]S[0-9]{5}L|(IT)?[0-9]{11}|(LT)?([0-9]{9}|[0-9]{12})|(LU)?[0-9]{8}|(LV)?[0-9]{11}|(MT)?[0-9]{8}|(NL)?[0-9]{9}B[0-9]{2}|(PL)?[0-9]{10}|(PT)?[0-9]{9}|(RO)?[0-9]{2,10}|(SE)?[0-9]{12}|(SI)?[0-9]{8}|(SK)?[0-9]{10})$/;
107const frenchVAT = regexEuropeanVATCodes.test('FRXX999999999'));
108
109// Test European Countries
110const regexEuropeanCountries = /AT|BE|BG|CY|CZ|DE|DK|EE|EL|GR|ES|FI|FR|GB|HU|IE|IT|LT|LU|LV|MT|NL|PL|PT|RO|SE|SI|SK/;
111
112// Everything from character to the end of the line (eg. good for find&replace)
113'.*
114
115// Find all numbers after the slash
116{ "appointments.bookingReference" : {$regex: "\/(525727)(?=[^\/]*$)", $options:"$i" } }
117