正则表达式或 regex 用于匹配字符串的各个部分. 下面是创建的正则表达式的备忘单.
测试正则表达式
使用该. test() 方法
- let testString = "My test string";
- let testRegex = /string/;
- testRegex.test(testString);
测试多项匹配
使用 OR 运算符 (|)
const regex = /yes|no|maybe/;
忽略大小写
使用 i 标志不区分大小写
- const caseInsensitiveRegex = /ignore case/i;
- const testString = 'We use the i flag to iGnOrE CasE';
- caseInsensitiveRegex.test(testString); // true
将第一个匹配提取到变量
使用该. match() 功能
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"]
匹配任何字符
使用通配符. 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"]
匹配具有多种可能性的单个字符
使用字符类, 您可以使用它来定义要匹配的一组字符
你把它们放在方括号内 []
- // 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
使用字符集中的范围 [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
要匹配你不希望有的字符集, 使用否定的字符集.
要排除字符集, 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
懒惰匹配
符合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? 角色进行懒惰匹配
- 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匹配, 请使用插入符号 ^, 但不要使用字符集
- 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
匹配结束字符串模式
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
- const emmaAtBackOfString = "The cats do not like Emma";
- const emmaNotAtBackOfString = "Emma loves the cats";
- const startingStringRegex = /Emma$/;
- startingStringRegex.test(emmaAtBackOfString); // true
- startingStringRegex.test(emmaNotAtBackOfString); // false
匹配所有字母和数字
使用 \ Word 速记
- const longHand = /[A-Za-z0-9_]+/;
- const shortHand = /\w+/;
- const numbers = "42";
- const myFavoriteColor = "magenta";
- longHand.test(numbers); // true
- shortHand.test(numbers); // true
- longHand.test(myFavoriteColor); // true
- shortHand.test(myFavoriteColor); // true
除了字母和数字之外的所有内容
您可以使用相反的 \ w 用 \ W
- const noAlphaNumericCharRegex = /\W/gi;
- const weirdCharacters = "!_$!!";
- 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], 也可以使用速记 \ 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
您可以使用相反的 \ d 用 \ D
- 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 匹配空格和回车
- const sentenceWithWhitespace = "I like cats!"
- var spaceRegex = /\s/g;
- whiteSpace.match(sentenceWithWhitespace); // [""," "]
匹配非空格
您可以使用相反的 \ s 用 \ 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
匹配最少的字符数
您只能定义最少数量的字符要求 {lowerBound,}
这称为数量说明符
- 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
匹配确切数量的字符数
您可以使用指定确切的字符要求数 {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
匹配全部或不匹配的字符
要检查字符是否存在, 请使用 ?
- const britishSpelling = "colour";
- const americanSpelling = "Color";
- const languageRegex = /colou?r/i;
- languageRegex.test(britishSpelling); // true
- languageRegex.test(americanSpelling); // true
来源: https://juejin.im/post/5c7496fdf265da2dda6957d2