71 lines
2.0 KiB
Markdown
71 lines
2.0 KiB
Markdown
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---
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id: bd7123c9c549eddfaeb5bdef
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title: Use Bracket Notation to Find the First Character in a String
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challengeType: 1
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videoUrl: ''
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localeTitle: 使用括号表示法查找字符串中的第一个字符
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---
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## Description
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<section id="description"> <code>Bracket notation</code>是一种在字符串中的特定<code>index</code>处获取字符的方法。大多数现代编程语言，如JavaScript，都不像人类那样开始计算。它们从0开始。这称为<dfn>基于零的</dfn>索引。例如，单词“Charles”中索引0处的字符是“C”。因此，如果<code>var firstName = "Charles"</code> ，则可以使用<code>firstName[0]</code>获取字符串第一个字母的值。 </section>
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## Instructions
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<section id="instructions">使用<dfn>括号表示法</dfn>查找<code>lastName</code>变量中的第一个字符并将其分配给<code>firstLetterOfLastName</code> 。 <strong>暗示</strong> <br>如果卡住，请尝试查看<code>firstLetterOfFirstName</code>变量声明。 </section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: <code>firstLetterOfLastName</code>变量的值应为<code>L</code>
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testString: 'assert(firstLetterOfLastName === "L", "The <code>firstLetterOfLastName</code> variable should have the value of <code>L</code>.");'
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- text: 您应该使用括号表示法。
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testString: 'assert(code.match(/firstLetterOfLastName\s*?=\s*?lastName\[.*?\]/), "You should use bracket notation.");'
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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// Example
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var firstLetterOfFirstName = "";
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var firstName = "Ada";
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firstLetterOfFirstName = firstName[0];
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// Setup
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var firstLetterOfLastName = "";
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var lastName = "Lovelace";
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// Only change code below this line
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firstLetterOfLastName = lastName;
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```
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</div>
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### After Test
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<div id='js-teardown'>
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```js
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console.info('after the test');
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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// solution required
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```
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</section>
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