JS 經常使用正則表達式備忘錄

匹配正則

使用 .test() 方法

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

匹配多個模式

使用操做符號 |

const regex = /yes|no|maybe/; 

忽略大小寫

使用i標誌表示忽略大小寫

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

提取變量的第一個匹配項

使用 .match() 方法

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

提取數組中的全部匹配項

使用 g 標誌

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

匹配任意字符

使用通配符. 做爲任何字符的佔位符

// 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"] 用多種可能性匹配單個字符

• 使用字符類，你能夠使用它來定義要匹配的一組字符

• 把它們放在方括號裏 []

//匹配 "cat" "fat" and "mat" 但不匹配 "bat"const regexWithCharClass = /[cfm]at/g;const testString = "cat fat bat mat";const allMatchingWords = testString.match(regexWithCharClass); // ["cat", "fat", "mat"] 

匹配字母表中的字母

使用字符集內的範圍 [a-z]​​​​​​​

const regexWidthCharRange = /[a-e]at/;const regexWithCharRange = /[a-e]at/;const catString = "cat";const batString = "bat";const fatString = "fat";regexWithCharRange.test(catString); // trueregexWithCharRange.test(batString); // trueregexWithCharRange.test(fatString); // false

匹配特定的數字和字母

你還能夠使用連字符來匹配數字​​​​​​​

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

匹配單個未知字符

要匹配您不想擁有的一組字符，使用否認字符集 ^​​​​​​​

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

匹配一行中出現一次或屢次的字符

使用 + 標誌​​​​​​​

const oneOrMoreAsRegex = /a+/gi;const oneOrMoreSsRegex = /s+/gi;const cityInFlorida = "Tallahassee";cityInFlorida.match(oneOrMoreAsRegex); // ['a', 'a', 'a'];cityInFlorida.match(oneOrMoreSsRegex); // ['ss'];   

匹配連續出現零次或屢次的字符

使用星號 *​​​​​​​

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

惰性匹配

• 字符串中與給定要求匹配的最小部分

• 默認狀況下，正則表達式是貪婪的（匹配知足給定要求的字符串的最長部分）

• 使用 ? 阻止貪婪模式(惰性匹配 )

 const testString = "catastrophe"; const greedyRexex = /c[a-z]*t/gi; const lazyRegex = /c[a-z]*?t/gi;  testString.match(greedyRexex); // ["catast"] testString.match(lazyRegex); // ["cat"] 

匹配起始字符串模式

要測試字符串開頭的字符匹配，請使用插入符號^，但要放大開頭，不要放到字符集中​​​​​​​

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

匹配結束字符串模式

使用 $ 來判斷字符串是不是以規定的字符結尾​​​​​​​

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

匹配全部字母和數字

使用\word 簡寫​​​​​​​​​​​​​​

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

除了字母和數字，其餘的都要匹配

用\W 表示 \w 的反義​​​​​​​

const noAlphaNumericCharRegex = /\W/gi;const weirdCharacters = "!_$!!";const alphaNumericCharacters = "ab283AD";noAlphaNumericCharRegex.test(weirdCharacters); // truenoAlphaNumericCharRegex.test(alphaNumericCharacters); // false

匹配全部數字

你能夠使用字符集[0-9]，或者使用簡寫 \d​​​​​​

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

匹配全部非數字

用\D 表示 \d 的反義​​​​​​​

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

匹配空格

使用 \s 來匹配空格和回車符​​​​​​​

const sentenceWithWhitespace = "I like cats!"var spaceRegex = /\s/g;whiteSpace.match(sentenceWithWhitespace); // [" ", " "]

匹配非空格

用\S 表示 \s 的反義​​​​​​​

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

匹配的字符數

你能夠使用 {下界，上界} 指定一行中的特定字符數​​​​​​​

const regularHi = "hi";const mediocreHi = "hiii";const superExcitedHey = "heeeeyyyyy!!!";const excitedRegex = /hi{1,4}/;excitedRegex.test(regularHi); // trueexcitedRegex.test(mediocreHi); // trueexcitedRegex.test(superExcitedHey); //false

匹配最低個數的字符數

使用{下界, }定義最少數量的字符要求,下面示例表示字母 i 至少要出現2次​​​​​​​

const regularHi = "hi";const mediocreHi = "hiii";const superExcitedHey = "heeeeyyyyy!!!";const excitedRegex = /hi{2,}/;excitedRegex.test(regularHi); // falseexcitedRegex.test(mediocreHi); // trueexcitedRegex.test(superExcitedHey); //false

匹配精確的字符數

使用{requiredCount}指定字符要求的確切數量​​​​​​​

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

匹配0次或1次

使用 ? 匹配字符 0 次或1次​​​​​​​

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