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This article mainly explains "what are the common regular expressions in JS". The content in the article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn what regular expressions are commonly used in JS.

Matching regularity

Use the .test () method

Let testString = "My test string"; let testRegex = / string/; testRegex.test (testString)

Match multiple patterns

Use action symbols |

Const regex = / yes | no | maybe/

Ignore case

Use the I flag to ignore case

Const caseInsensitiveRegex = / ignore case/i; const testString ='We use the i flag to iGnOrE CasE'; caseInsensitiveRegex.test (testString); / / true

Extract * matches of variables

Use the .match () method

Const match = "Hello World!" .match (/ hello/i); / / "Hello"

Extract all matches in the array

Use the g flag

Const testString = "Repeat repeat rePeAT"; const regexWithAllMatches = / Repeat/gi; testString.match (regexWithAllMatches); / / ["Repeat", "repeat", "rePeAT"]

Match any character

Use wildcards. As a placeholder for any character

/ / To match "cat", "BAT", "fAT", "mat" const regexWithWildcard = / .at / gi; const testString = "cat BAT cupcake fAT mat dog"; const allMatchingWords = testString.match (regexWithWildcard); / / ["cat", "BAT", "fAT", "mat"]

Match a single character with multiple possibilities

Using a character class, you can use it to define a set of characters to match

Put them in square brackets []

/ match "cat"fat" and "mat" but not "bat" const regexWithCharClass = / [cfm] at/g; const testString = "cat fat bat mat"; const allMatchingWords = testString.match (regexWithCharClass); / / ["cat", "fat", "mat"]

Match the letters in the alphabet

Use the range within the character set [amurz]

Const regexWidthCharRange = / [a mure] at/; const regexWithCharRange = / [a mure] at/; const catString = "cat"; const batString = "bat"; const fatString = "fat"; regexWithCharRange.test (catString); / / true regexWithCharRange.test (batString); / / true regexWithCharRange.test (fatString); / / false

Match specific numbers and letters

You can also use hyphens to match numbers

Const regexWithLetterAndNumberRange = / [a-z0-9] / ig; const testString = "Emma19382"; testString.match (regexWithLetterAndNumberRange) / / true

Match a single unknown character

To match a set of characters you don't want to have, use the negative character set ^

Const allCharsNotVowels = / [^ aeiou] / gi; const allCharsNotVowelsOrNumbers = / [^ aeiou0-9] / gi

Matches characters that appear one or more times on a line

Use the + flag

Const oneOrMoreAsRegex = / aura oneOrMoreSsRegex; const oneOrMoreSsRegex = / swarm plagma g; const cityInFlorida = "Tallahassee"; cityInFlorida.match (oneOrMoreAsRegex); / / ['a','a','a']; cityInFlorida.match (oneOrMoreSsRegex); / / ['ss']

Matches characters that appear zero or more times in a row

Use an asterisk *

Const zeroOrMoreOsRegex = / hi*/gi; const normalHi = "hi"; const happyHi = "hiiiiii"; const twoHis = "hiihii"; const bye = "bye"; normalHi.match (zeroOrMoreOsRegex); / / ["hi"] happyHi.match (zeroOrMoreOsRegex); / / ["hiiiiii"] twoHis.match (zeroOrMoreOsRegex); / / [hii "," hii "] bye.match (zeroOrMoreOsRegex); / / null

Lazy matching

The smallest part of a string that matches a given requirement

By default, regular expressions are greedy (matching the longest part of a string that meets a given requirement)

Use? Block greedy mode (lazy matching)

Const testString = "catastrophe"; const greedyRexex = / c [a Murz] * t Unigo; const lazyRegex = / c [a Muyz] *? t Maple g; testString.match (greedyRexex); / / ["catast"] testString.match (lazyRegex); / / ["cat"]

Match starting string pattern

To test for character matching at the beginning of a string, use the caret ^, but to enlarge the beginning, do not put it in the character set

Const emmaAtFrontOfString = "Emma likes cats a lot."; const emmaNotAtFrontOfString = "The cats Emma likes are fluffy."; const startingStringRegex = / ^ Emma/; startingStringRegex.test (emmaAtFrontOfString); / / true startingStringRegex.test (emmaNotAtFrontOfString); / / false

Match end string pattern

Use $to determine whether a string ends with a specified character

Const emmaAtBackOfString = "The cats do not like Emma"; const emmaNotAtBackOfString = "Emma loves the cats"; const startingStringRegex = / Emma$/; startingStringRegex.test (emmaAtBackOfString); / / true startingStringRegex.test (emmaNotAtBackOfString); / / false

Match all letters and numbers

Use the abbreviation\ word

Const longHand = / [A-Za-z0-9 _] + /; const shortHand = /\ wigzag; const numbers = "42"; const myFavoriteColor = "magenta"; longHand.test (numbers); / / true shortHand.test (numbers); / / true longHand.test (myFavoriteColor); / / true shortHand.test (myFavoriteColor); / / true

Everything has to match except letters and numbers

Use\ W to represent the antonym of\ w

Const noAlphaNumericCharRegex = /\ Whamgi; const weirdCharacters = "! _ $!!"; const alphaNumericCharacters = "ab283AD"; noAlphaNumericCharRegex.test (weirdCharacters); / / true noAlphaNumericCharRegex.test (alphaNumericCharacters); / / false

Match all numbers

You can use the character set [0-9], or use the abbreviation\ d

Const digitsRegex = /\ d worth of food a week; const stringWithDigits = "My cat eats $20.00 worth of food a week."; stringWithDigits.match (digitsRegex); / / ["2", "0", "0", "0"]

Match all non-digits

Use\ D to represent the antonym of\ d

Const nonDigitsRegex = /\ DWeig; const stringWithLetters = "101 degrees"; stringWithLetters.match (nonDigitsRegex); / / ["", "d", "e", "g", "r", "e", "e", "s"]

Match Spac

Use\ s to match spaces and carriage returns

Const sentenceWithWhitespace = "I like cats!" Var spaceRegex = /\ sUnig; whiteSpace.match (sentenceWithWhitespace); / / [","]

Match non-space

Use\ S to represent the antonym of\ s

Const sentenceWithWhitespace = "C at" const nonWhiteSpaceRegex = /\ S nonWhiteSpaceRegex g; sentenceWithWhitespace.match (nonWhiteSpaceRegex); / / ["C", "a", "t"]

Number of characters matched

You can use {lower bound, upper bound} to specify a specific number of characters in a line

Const regularHi = "hi"; const mediocreHi = "hiii"; const superExcitedHey = "heeeeyyyyybeans!"; const excitedRegex = / hi {1je 4} /; excitedRegex.test (regularHi); / / true excitedRegex.test (mediocreHi); / / true excitedRegex.test (superExcitedHey); / / false

The number of characters that match the number of

Use {lower bound,} to define a minimum number of character requirements. The following example indicates that the letter I must appear at least twice.

Const regularHi = "hi"; const mediocreHi = "hiii"; const superExcitedHey = "heeeeyyyyybeans!"; const excitedRegex = / hi {2,} /; excitedRegex.test (regularHi); / / false excitedRegex.test (mediocreHi); / / true excitedRegex.test (superExcitedHey); / / false

Match the exact number of characters

Use {requiredCount} to specify the exact number of characters required

Const regularHi = "hi"; const bestHi = "hii"; const mediocreHi = "hiii"; const excitedRegex = / hi {2} /; excitedRegex.test (regularHi); / / false excitedRegex.test (bestHi); / / true excitedRegex.test (mediocreHi); / / false

Match 0 times or 1 time

Use? Match characters 0 or 1 times

Const britishSpelling = "colour"; const americanSpelling = "Color"; const languageRegex = / colou?r/i; languageRegex.test (britishSpelling); / / true languageRegex.test (americanSpelling); / / true

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