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access-an-arrays-contents-using-bracket-notation.chinese.md
access-property-names-with-bracket-notation.chinese.md
add-items-to-an-array-with-push-and-unshift.chinese.md
add-items-using-splice.chinese.md
add-key-value-pairs-to-javascript-objects.chinese.md
check-for-the-presence-of-an-element-with-indexof.chinese.md
check-if-an-object-has-a-property.chinese.md
combine-arrays-with-the-spread-operator.chinese.md
copy-an-array-with-the-spread-operator.chinese.md
copy-array-items-using-slice.chinese.md
create-complex-multi-dimensional-arrays.chinese.md
generate-an-array-of-all-object-keys-with-object.keys.chinese.md
iterate-through-all-an-arrays-items-using-for-loops.chinese.md
iterate-through-the-keys-of-an-object-with-a-for...in-statement.chinese.md
modify-an-array-stored-in-an-object.chinese.md
modify-an-object-nested-within-an-object.chinese.md
remove-items-from-an-array-with-pop-and-shift.chinese.md
remove-items-using-splice.chinese.md
use-an-array-to-store-a-collection-of-data.chinese.md
use-the-delete-keyword-to-remove-object-properties.chinese.md
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60 lines
3.0 KiB
Markdown
60 lines
3.0 KiB
Markdown
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---
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id: 5a661e0f1068aca922b3ef17
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title: Access an Array's Contents Using Bracket Notation
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challengeType: 1
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videoUrl: ''
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localeTitle: 使用括号表示法访问数组的内容
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---
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## Description
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<section id="description">当然，任何数据结构的基本特征是不仅能够存储数据，而且能够根据命令检索该数据。所以，既然我们已经学会了如何创建数组，那么让我们开始考虑如何访问该数组的信息。当我们定义一个如下所示的简单数组时，其中有3个项目： <blockquote>让ourArray = [“a”，“b”，“c”]; </blockquote>在数组中，每个数组项都有一个<dfn>索引</dfn> 。此索引兼作数组中该项的位置，以及您如何引用它。但是，值得注意的是，JavaScript数组是<dfn>零索引的</dfn> ，这意味着数组的第一个元素实际上处于第<em><strong>零</strong></em>位，而不是第一个。为了从数组中检索元素，我们可以将一个索引括在括号中，并将其附加到数组的末尾，或者更常见的是附加到引用数组对象的变量。这称为<dfn>括号表示法</dfn> 。例如，如果我们想从<code>ourArray</code>检索<code>"a"</code>并将其分配给变量，我们可以使用以下代码执行此操作： <blockquote>让ourVariable = ourArray [0]; <br> // ourVariable等于“a” </blockquote>除了访问与索引相关的值，你还可以<em>设置</em>索引使用相同的符号中的值： <blockquote> ourArray [1] =“不再是b”; <br> // ourArray现在等于[“a”，“不再b”，“c”]; </blockquote>使用括号表示法，我们现在将索引1处的项目从<code>"b"</code>重置为<code>"not b anymore"</code> 。 </section>
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## Instructions
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<section id="instructions">为了完成此挑战，将<code>myArray</code>的第二个位置（索引<code>1</code> ）设置为您想要的任何内容，除了<code>"b"</code> 。 </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>myArray[0]</code>等于<code>"a"</code>'
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testString: 'assert.strictEqual(myArray[0], "a", "<code>myArray[0]</code> is equal to <code>"a"</code>");'
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- text: '<code>myArray[1]</code>不再设置为<code>"b"</code>'
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testString: 'assert.notStrictEqual(myArray[1], "b", "<code>myArray[1]</code> is no longer set to <code>"b"</code>");'
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- text: '<code>myArray[2]</code>等于<code>"c"</code>'
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testString: 'assert.strictEqual(myArray[2], "c", "<code>myArray[2]</code> is equal to <code>"c"</code>");'
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- text: '<code>myArray[3]</code>等于<code>"d"</code>'
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testString: 'assert.strictEqual(myArray[3], "d", "<code>myArray[3]</code> is equal to <code>"d"</code>");'
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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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let myArray = ["a", "b", "c", "d"];
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// change code below this line
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//change code above this line
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console.log(myArray);
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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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