72 lines
1.7 KiB
Markdown
72 lines
1.7 KiB
Markdown
---
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id: 587d7db7367417b2b2512b9d
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title: 匹配字符串的开头
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challengeType: 1
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forumTopicId: 301349
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dashedName: match-beginning-string-patterns
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---
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# --description--
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回顾一下之前的挑战，正则表达式可以用于查找多项匹配。还可以查询字符串中符合指定匹配模式的字符。
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在之前的挑战中，使用`字符集`中的`插入`符号（`^`）来创建一个`否定字符集`，形如`[^thingsThatWillNotBeMatched]`。在`字符集`之外，`插入`符号用于字符串的开头搜寻匹配模式。
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```js
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let firstString = "Ricky is first and can be found.";
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let firstRegex = /^Ricky/;
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firstRegex.test(firstString);
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// Returns true
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let notFirst = "You can't find Ricky now.";
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firstRegex.test(notFirst);
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// Returns false
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```
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# --instructions--
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在正则表达式中使用`^`符号，以匹配仅在字符串`rickyAndCal`的开头出现的`"Cal"`。
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# --hints--
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你的正则表达式应该搜寻有一个大写字母的`'Cal'`。
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```js
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assert(calRegex.source == '^Cal');
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```
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你的正则表达式不应该使用任何标志。
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```js
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assert(calRegex.flags == '');
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```
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你的正则表达式应该匹配字符串开头的`'Cal'`。
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```js
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assert(calRegex.test('Cal and Ricky both like racing.'));
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```
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你的正则表达式不应该匹配字符串中间的`'Cal'`。
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```js
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assert(!calRegex.test('Ricky and Cal both like racing.'));
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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 rickyAndCal = "Cal and Ricky both like racing.";
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let calRegex = /change/; // Change this line
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let result = calRegex.test(rickyAndCal);
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```
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# --solutions--
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```js
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let rickyAndCal = "Cal and Ricky both like racing.";
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let calRegex = /^Cal/; // Change this line
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let result = calRegex.test(rickyAndCal);
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```
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