我使用正規表示式的經驗
我一直遠離正規表示式。在我第一年的電腦科學實驗室中，有一個涉及正規表示式的練習。我想那是我第一次被介紹給它。我當時認為這很酷，但看起來太難了，所以我一直在避免它，或者只是在谷歌上搜尋如何解決某個正規表示式問題。但我終於花了一些時間來正確學習它🎉
在閱讀了一些資源並涉獵之後，可以肯定地說我不再害怕正規表示式了！我發現自己在我所做的許多編碼練習中都使用了它。所需要的只是練習！以下是我根據我學到的正規表示式和我使用的資源編寫的備忘單（帶有範例）
備忘錄
我已經包含了一些我學到的 Javascript 中不可用的正規表示式。對於這些，我都註解掉了。如果需要的話請記住「g」修飾符！對於我的範例，我省略了修飾符。
let regex;
/* matching a specific string */
regex = /hello/; // looks for the string between the forward slashes (case-sensitive)... matches "hello", "hello123", "123hello123", "123hello"; doesn't match for "hell0", "Hello"
regex = /hello/i; // looks for the string between the forward slashes (case-insensitive)... matches "hello", "HelLo", "123HelLO"
regex = /hello/g; // looks for multiple occurrences of string between the forward slashes...
/* wildcards */
regex = /h.llo/; // the "." matches any one character other than a new line character... matches "hello", "hallo" but not "h\nllo"
regex = /h.*llo/; // the "*" matches any character(s) zero or more times... matches "hello", "heeeeeello", "hllo", "hwarwareallo"
/* shorthand character classes */
regex = /\d/; // matches any digit
regex = /\D/; // matches any non-digit
regex = /\w/; // matches any word character (a-z, A-Z, 0-9, _)
regex = /\W/; // matches any non-word character
regex = /\s/; // matches any white space character (\r (carriage return),\n (new line), \t (tab), \f (form feed))
regex = /\S/; // matches any non-white space character
/* specific characters */
regex = /[aeiou]/; // matches any character in square brackets
regex = /[ck]atherine/; // matches catherine or katherine
regex = /[^aeiou]/; // matches anything except the characters in square brackets
/* character ranges */
regex = /[a-z]/; // matches all lowercase letters
regex = /[A-Z]/; // matches all uppercase letters
regex = /[e-l]/; // matches lowercase letters e to l (inclusive)
regex = /[F-P]/; // matches all uppercase letters F to P (inclusive)
regex = /[0-9]/; // matches all digits
regex = /[5-9]/; // matches any digit from 5 to 9 (inclusive)
regex = /[a-zA-Z]/; // matches all lowercase and uppercase letters
regex = /[^a-zA-Z]/; // matches non-letters
/* matching repetitions using quantifiers */
regex = /(hello){4}/; // matches "hellohellohellohello"
regex = /hello{3}/; // matches "hellooo" and "helloooo" but not "helloo"
regex = /\d{3}/; // matches 3 digits ("312", "122", "111", "12312321" but not "12")
regex = /\d{3,7}/; // matches digits that occur between 3 and 7 times (inclusive)
regex = /\d{3,}/; // matches digits that occur at least 3 times
/* matching repetitions using star and plus */
regex = /ab*c/; // matches zero or more repetitions of "b" (matches "abc", "abbbbc", "ac")
regex = /ab+c/; // matches one or more repetitions of "b" (matches "abc", "abbbbc", but not "ac")
/* matching beginning and end items */
regex = /^[A-Z]\w*/; // matches "H", "Hello", but not "hey"
regex = /\w*s$/; // matches "cats", "dogs", "avocados", but not "javascript"
/* matching word boundaries
positions of word boundaries:
1. before the first character in string (if first character is a word character)
2. after the last character in the string, if the last character is a word character
3. between two characters in string, where one is a word character and the other isn't */
regex = /\bmeow\b/; // matches "hey meow lol", "hey:meow:lol", but not "heymeow lol"
/* groups */
regex = /it is (ice )?cold outside/; // matches "it is ice cold outside" and "it is cold outside"
regex = /it is (?:ice )?cold outside/; // same as above except it is a non-capturing group
regex = /do (cats) like taco \1/; // matches "do cats like taco cats"
regex = /do (cats) like (taco)\? do \2 \1 like you\?/; // matches "do cats like taco? do taco cats like you?"
//branch reset group (available in Perl, PHP, R, Delphi... commented out because this is a js file)
// regex = /(?|(cat)|(dog))\1/; // matches "catcat" and "dogdog"
/* alternative matching */
regex = /i like (tacos|boba|guacamole)\./; // matches "i like tacos.", "i like boba.", and "i like guacamole."
/* forward reference (available in Perl, PHP, Java, Ruby, etc... commented out because this is a js file) */
// regex = /(\2train|(choo))+/; // matches "choo", "choochoo", "chootrain", choochootrain", but not "train"
/* lookaheads */
regex = /z(?=a)/; // positive lookahead... matches the "z" before the "a" in pizza" but not the first "z"
regex = /z(?!a)/; // negative lookahead... matches the first "z" but not the "z" before the "a"
/* lookbehinds */
regex = /(?<=[aeiou])\w/; // positive lookbehind... matches any word character that is preceded by a vowel
regex = /(?<![aeiou])\w/; // negative lookbehind... matches any word character that is not preceded by a vowel
/* functions I find useful */
regex.test("hello"); // returns true if found a match, false otherwise
regex.exec("hello"); // returns result array, null otherwise
"football".replace(/foot/,"basket"); // replaces matches with second argument
感謝 Sarthak 建立了我的備忘錄的GitHub 要點，也感謝 Xian-an 將其翻譯成中文👏
資源
「正規表示式」挑戰是FreeCodeCamp上「Javascript 演算法和資料結構認證」的一部分
Regex101用於測試（您也可以使用 Chrome 開發者控制台）
HackerRank正規表示式挑戰練習
就是這樣，夥計們！希望這對您有幫助☺️
原文出處：https://dev.to/catherinecodes/a-regex-cheatsheet-for-all-those-regex-haters-and-lovers--2cj1
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