标签：eee 判断 activity 集中 大小 符号 回车符 贪婪 正则
使用 .test() 方法
let testString = "My test string";let testRegex = /string/;testRegex.test(testString);
使用操作符号 |
const regex = /yes|no|maybe/;
使用i标志表示忽略大小写
const caseInsensitiveRegex = /ignore case/i;const testString = ‘We use the i flag to iGnOrE CasE‘;caseInsensitiveRegex.test(testString); // true
使用 .match() 方法
const match = "Hello World!".match(/hello/i); // "Hello"
使用 g 标志
const testString = "Repeat repeat rePeAT";const regexWithAllMatches = /Repeat/gi;testString.match(regexWithAllMatches); // ["Repeat", "repeat", "rePeAT"]
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"] 用多种可能性匹配单个字符
1）使用字符类，你可以使用它来定义要匹配的一组字符
2）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"]
使用字符集内的范围 [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
你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
要匹配您不想拥有的一组字符，使用否定字符集 ^
const allCharsNotVowels = /[^aeiou]/gi;const allCharsNotVowelsOrNumbers = /[^aeiou0-9]/gi;
使用 + 标志
const oneOrMoreAsRegex = /a+/gi;const oneOrMoreSsRegex = /s+/gi;const cityInFlorida = "Tallahassee"; cityInFlorida.match(oneOrMoreAsRegex); // [‘a‘, ‘a‘, ‘a‘];cityInFlorida.match(oneOrMoreSsRegex); // [‘ss‘];
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
1）字符串中与给定要求匹配的最小部分
2）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）
3）使用 ? 阻止贪婪模式(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
要测试字符串开头的字符匹配，请使用插入符号^，但要放大开头，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
使用 $ 来判断字符串是否是以规定的字符结尾
const emmaAtBackOfString = "The cats do not like Emma";const emmaNotAtBackOfString = "Emma loves the cats";const startingStringRegex = /Emma$/; startingStringRegex.test(emmaAtBackOfString); // truestartingStringRegex.test(emmaNotAtBackOfString); // false
使用\word 简写
const longHand = /[A-Za-z0-9_]+/;const shortHand = /\w+/;const numbers = "42";const myFavoriteColor = "magenta"; longHand.test(numbers); // trueshortHand.test(numbers); // truelongHand.test(myFavoriteColor); // trueshortHand.test(myFavoriteColor); // true
用\W 表示 \w 的反义
const noAlphaNumericCharRegex = /\W/gi;const weirdCharacters = "!_$!!";const alphaNumericCharacters = "ab283AD"; noAlphaNumericCharRegex.test(weirdCharacters); // truenoAlphaNumericCharRegex.test(alphaNumericCharacters); // false
你可以使用字符集[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"]
用\D 表示 \d 的反义
const nonDigitsRegex = /\D/g;const stringWithLetters = "101 degrees"; stringWithLetters.match(nonDigitsRegex); // [" ", "d", "e", "g", "r", "e", "e", "s"]
使用 \s 来匹配空格和回车符
const sentenceWithWhitespace = "I like cats!"var spaceRegex = /\s/g;whiteSpace.match(sentenceWithWhitespace); // [" ", " "]
用\S 表示 \s 的反义
const sentenceWithWhitespace = "C a t"const nonWhiteSpaceRegex = /\S/g;sentenceWithWhitespace.match(nonWhiteSpaceRegex); // ["C", "a", "t"]
你可以使用 {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); // trueexcitedRegex.test(mediocreHi); // trueexcitedRegex.test(superExcitedHey); //false
使用{下界, }定义最少数量的字符要求,下面示例表示字母 i 至少要出现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
使用{requiredCount}指定字符要求的确切数量
const regularHi = "hi";const bestHi = "hii";const mediocreHi = "hiii";const excitedRegex = /hi{2}/;
excitedRegex.test(regularHi); // falseexcitedRegex.test(bestHi); // trueexcitedRegex.test(mediocreHi); //false
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
标签：eee 判断 activity 集中 大小 符号 回车符 贪婪 正则
原文地址：https://www.cnblogs.com/Michelle20180227/p/10921893.html
