JS常用正则表达式备忘录

　　匹配正则

　　运用 .test() 办法

let testString = "My test string";

let testRegex = /string/;

testRegex.test(testString);

　　匹配多个方式

　　运用操作符号 |

const regex = /yes|no|maybe/;

　　疏忽大小写

　　运用i标志表明疏忽大小写

const caseInsensitiveRegex = /ignore case/i;

const testString = 'We use the i flag to iGnOrE CasE';

caseInsensitiveRegex.test(testString); // true

　　提取变量的第一个匹配项

　　运用 .match() 办法

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

　　提取数组中的一切匹配项

　　运用 g 标志

const testString = "Repeat repeat rePeAT";

const regexWithAllMatches = /Repeat/gi;

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

　　匹配恣意字符

　　运用通配符. 作为任何字符的占位符

// 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"]

　　用多种或许性匹配单个字符

　　运用字符类，你能够运用它来界说要匹配的一组字符

　　把它们放在方括号里 []

//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

　　运用字符集内的规模 [a-z]

const regexWidthCharRange = /[a-e]at/;

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

　　你还能够运用连字符来匹配数字

const regexWithLetterAndNumberRange = /[a-z0-9]/ig;

const testString = "Emma19382";

testString.match(regexWithLetterAndNumberRange) // true

　　匹配单个不知道字符

　　要匹配您不想具有的一组字符，运用否定字符集 ^

const allCharsNotVowels = /[^aeiou]/gi;

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

　　匹配一行中呈现一次或屡次的字符

　　运用 + 标志

const oneOrMoreAsRegex = /a+/gi;

const oneOrMoreSsRegex = /s+/gi;

const cityInFlorida = "Tallahassee";

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

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

　　匹配接连呈现零次或屡次的字符

　　运用星号 *

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

　　慵懒匹配

　　字符串中与给定要求匹配的最小部分

　　默许情况下，正则表达式是贪婪的（匹配满意给定要求的字符串的最长部分）

　　运用 ? 阻挠贪婪方式(慵懒匹配 )

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"]

　　匹配开始字符串方式

　　要测验字符串最初的字符匹配，请运用刺进符号^，但要扩大最初，不要放到字符会集

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

　　匹配完毕字符串方式

　　运用 $ 来判别字符串是否是以规则的字符完毕

onst emmaAtBackOfString = "The cats do not like Emma";

const emmaNotAtBackOfString = "Emma loves the cats";

const startingStringRegex = /Emma$/;

startingStringRegex.test(emmaAtBackOfString); // true

startingStringRegex.test(emmaNotAtBackOfString); // false

　　匹配一切字母和数字

　　运用\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

　　除了字母和数字，其他的都要匹配

　　用\W 表明 \w 的反义

const noAlphaNumericCharRegex = /\W/gi;

const weirdCharacters = "!_$!!";

const alphaNumericCharacters = "ab283AD";

noAlphaNumericCharRegex.test(weirdCharacters); // true

noAlphaNumericCharRegex.test(alphaNumericCharacters); // false

　　匹配一切数字

　　你能够运用字符集[0-9]，或许运用简写 \d

const digitsRegex = /\d/g;

const stringWithDigits = "My cat eats $20.00 worth of food a week.";

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

　　匹配一切非数字

　　用\D 表明 \d 的反义

const nonDigitsRegex = /\D/g;

const stringWithLetters = "101 degrees";

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

　　匹配空格

　　运用 \s 来匹配空格和回车符

const sentenceWithWhitespace = "I like cats!"

var spaceRegex = /\s/g;

whiteSpace.match(sentenceWithWhitespace); // [" ", " "]

　　匹配非空格

　　用\S 表明 \s 的反义

const sentenceWithWhitespace = "C a t"

const nonWhiteSpaceRegex = /\S/g;

sentenceWithWhitespace.match(nonWhiteSpaceRegex); // ["C", "a", "t"]

　　匹配的字符数

　　你能够运用 {下界，上界} 指定一行中的特定字符数

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

　　匹配最低个数的字符数

　　运用{下界, }界说最少数量的字符要求,下面示例表明字母 i 至少要呈现2次

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

　　匹配准确的字符数

　　运用{requiredCount}指定字符要求的切当数量

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0次或1次

　　运用 ? 匹配字符 0 次或1次

const britishSpelling = "colour";

const americanSpelling = "Color";

const languageRegex = /colou?r/i;

languageRegex.test(britishSpelling); // true

languageRegex.test(americanSpelling); // true