99 lines
2.5 KiB
Markdown
99 lines
2.5 KiB
Markdown
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---
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id: 587d7db7367417b2b2512b9f
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title: 匹配所有的字母和數字
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challengeType: 1
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forumTopicId: 301346
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dashedName: match-all-letters-and-numbers
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---
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# --description--
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使用元字符，可以使用 `[a-z]` 搜尋字母表中的所有字母。 這種元字符是很常見的，它有一個縮寫，但這個縮寫也包含額外的字符。
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JavaScript 中與字母表匹配的最接近的元字符是`\w`。 這個縮寫等同於`[A-Za-z0-9_]`。 此字符類匹配上面字母和小寫字母以及數字。 注意，這個字符類也包含下劃線字符 (`_`)。
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```js
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let longHand = /[A-Za-z0-9_]+/;
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let shortHand = /\w+/;
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let numbers = "42";
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let varNames = "important_var";
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longHand.test(numbers);
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shortHand.test(numbers);
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longHand.test(varNames);
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shortHand.test(varNames);
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```
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上面的 `test` 都會返回 `true`。
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這些元字符縮寫也被稱爲短語元字符 <dfn>shorthand character classes</dfn>。
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# --instructions--
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使用元字符 `\w` 來計算所有引號中字母和數字字符的數量。
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# --hints--
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您的正則表達式應該使用全局標識。
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```js
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assert(alphabetRegexV2.global);
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```
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正則表達式應該使用元字符r `\w` 來匹配非字母字符。
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```js
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assert(/\\w/.test(alphabetRegexV2.source));
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```
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你的正則表達式應該在 `The five boxing wizards jump quickly.` 中匹配到 31 個非字母數字字符。
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```js
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assert(
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'The five boxing wizards jump quickly.'.match(alphabetRegexV2).length === 31
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);
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```
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你的正則表達式應該在 `Pack my box with five dozen liquor jugs.` 中匹配到 32 個非字母數字字符。
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```js
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assert(
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'Pack my box with five dozen liquor jugs.'.match(alphabetRegexV2).length ===
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32
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);
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```
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你的正則表達式應該在 `How vexingly quick daft zebras jump!` 中匹配到 30 個非字母數字字符。
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```js
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assert(
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'How vexingly quick daft zebras jump!'.match(alphabetRegexV2).length === 30
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);
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```
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你的正則表達式應該在字符串 `123 456 7890 ABC def GHI jkl MNO pqr STU vwx YZ.` 中找到36個字母數字字符。
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```js
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assert(
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'123 456 7890 ABC def GHI jkl MNO pqr STU vwx YZ.'.match(alphabetRegexV2)
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.length === 36
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);
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```
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# --seed--
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## --seed-contents--
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```js
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let quoteSample = "The five boxing wizards jump quickly.";
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let alphabetRegexV2 = /change/; // Change this line
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let result = quoteSample.match(alphabetRegexV2).length;
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```
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# --solutions--
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```js
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let quoteSample = "The five boxing wizards jump quickly.";
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let alphabetRegexV2 = /\w/g; // Change this line
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let result = quoteSample.match(alphabetRegexV2).length;
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```
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