正则表达式速查表

正则表达式（或称“regex”）用于匹配字符串的各个部分。以下是我创建正则表达式的速查表。

测试正则表达式

使用.test()方法

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

测试多种模式

使用或运算符 (|)

const regex = /yes|no|maybe/;

忽略大小写

使用i不区分大小写的标志

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

将第一个匹配项提取到变量

使用.match()函数

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

提取数组中的所有匹配项

使用g标志

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.作为任意字符的占位符

// 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"]

匹配单个字符的多种可能性

使用字符类，它允许您定义一组想要匹配的字符
你把它们放在方括号里[]

// 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"]

匹配字母表的字母

使用字符集内的范围[a-z]

const regexWithCharRange = /[a-e]at/;
const catString = "cat";
const batString = "bat";
const fatString = "fat";

regexWithCharRange.test(catString); // true
regexWithCharRange.test(batString); // true
regexWithCharRange.test(fatString); // false

匹配特定的数字和字母

您还可以使用连字符来匹配数字

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

匹配单个未知字符

要匹配一组你不想要的字符，请使用否定字符集
要否定字符集，请使用插入符号^

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

匹配连续出现一次或多次的字符

使用+符号

const oneOrMoreAsRegex = /a+/gi;
const oneOrMoreSsRegex = /s+/gi;
const cityInFlorida = "Tallahassee";

cityInFlorida.match(oneOrMoreAsRegex); // ['a', 'a', 'a'];
cityInFlorida.match(oneOrMoreSsRegex); // ['ss'];

匹配连续出现零次或多次的字符

使用星号*

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

满足给定要求的字符串的最小部分
默认情况下，正则表达式是贪婪的（匹配满足给定要求的字符串的最长部分）
使用?字符进行惰性匹配

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

要测试字符串开头的字符是否匹配，请使用插入符号^，但要在字符集之外

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

匹配结尾字符串模式

使用正则表达式末尾的美元符号$来检查字符串末尾是否存在模式

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

匹配所有字母和数字

使用\word简写

const longHand = /[A-Za-z0-9_]+/;
const shortHand = /\w+/;
const numbers = "42";
const myFavoriteColor = "magenta";

longHand.test(numbers); // true
shortHand.test(numbers); // true
longHand.test(myFavoriteColor); // true
shortHand.test(myFavoriteColor); // true

匹配除字母和数字之外的所有内容

\w你可以使用与\W

const noAlphaNumericCharRegex = /\W/gi;
const weirdCharacters = "!_$!!";
const alphaNumericCharacters = "ab283AD";

noAlphaNumericCharRegex.test(weirdCharacters); // true
noAlphaNumericCharRegex.test(alphaNumericCharacters); // false

匹配所有数字

您可以使用字符集[0-9]，或者使用简写\d

const digitsRegex = /\d/g;
const stringWithDigits = "My cat eats $20.00 worth of food a week.";

stringWithDigits.match(digitsRegex); // ["2", "0", "0", "0"]

匹配所有非数字

你可以使用\d与\D

const nonDigitsRegex = /\D/g;
const stringWithLetters = "101 degrees";

stringWithLetters.match(nonDigitsRegex); // [" ", "d", "e", "g", "r", "e", "e", "s"]

匹配空格

用于\s匹配空格和回车符

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

匹配非空白

你可以使用\s与\S

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

匹配字符数

您可以使用以下方式指定一行中的特定字符数{lowerBound, upperBound}

const regularHi = "hi";
const mediocreHi = "hiii";
const superExcitedHey = "heeeeyyyyy!!!";
const excitedRegex = /hi{1,4}/;

excitedRegex.test(regularHi); // true
excitedRegex.test(mediocreHi); // true
excitedRegex.test(superExcitedHey); //false

匹配最低字符数

您只能使用以下方式定义最少数量的字符要求{lowerBound,}
这被称为数量说明符

const regularHi = "hi";
const mediocreHi = "hiii";
const superExcitedHey = "heeeeyyyyy!!!";
const excitedRegex = /hi{2,}/;

excitedRegex.test(regularHi); // false
excitedRegex.test(mediocreHi); // true
excitedRegex.test(superExcitedHey); //false

匹配精确的字符数

您可以使用以下方式指定确切的字符数要求{requiredCount}

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

匹配全部或不匹配字符

要检查某个字符是否存在，请使用?

const britishSpelling = "colour";
const americanSpelling = "Color";
const languageRegex = /colou?r/i;

languageRegex.test(britishSpelling); // true
languageRegex.test(americanSpelling); // true

文章来源：https://dev.to/emmabostian/regex-cheat-sheet-2j2a