freeCodeCamp/curriculum/challenges/chinese/02-javascript-algorithms-and-data-structures/basic-javascript/accessing-nested-arrays.md

---
id: 56533eb9ac21ba0edf2244cd
challengeType: 1
videoUrl: 'https://scrimba.com/c/cLeGDtZ'
forumTopicId: 16160
localeTitle: 访问嵌套数组
---

## Description
<section id='description'>
正如我们在前面的例子所见，对象可以嵌套对象和数组。与访问嵌套对象一样，用中括号操作符同样可以访问嵌套数组。
下面是如何访问嵌套数组的例子：

```js
var ourPets = [
  {
    animalType: "cat",
    names: [
      "Meowzer",
      "Fluffy",
      "Kit-Cat"
    ]
  },
  {
    animalType: "dog",
    names: [
      "Spot",
      "Bowser",
      "Frankie"
    ]
  }
];
ourPets[0].names[1]; // "Fluffy"
ourPets[1].names[0]; // "Spot"
```

</section>

## Instructions
<section id='instructions'>
使用点操作符和中括号操作符来检索变量<code>myPlants</code>的第二棵树。
</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: <code>secondTree</code>应该等于 "pine"。
    testString: assert(secondTree === "pine");
  - text: 使用点操作符和中括号操作符来检索变量<code>myPlants</code>。
    testString: assert(/=\s*myPlants\[1\].list\[1\]/.test(code));

```

</section>

## Challenge Seed
<section id='challengeSeed'>

<div id='js-seed'>

```js
// Setup
var myPlants = [
  {
    type: "flowers",
    list: [
      "rose",
      "tulip",
      "dandelion"
    ]
  },
  {
    type: "trees",
    list: [
      "fir",
      "pine",
      "birch"
    ]
  }
];

// Only change code below this line

var secondTree = ""; // Change this line

```

</div>


### After Test
<div id='js-teardown'>

```js
(function(x) {
  if(typeof x != 'undefined') {
    return "secondTree = " + x;
  }
  return "secondTree is undefined";
})(secondTree);
```

</div>

</section>

## Solution
<section id='solution'>


```js
var myPlants = [
  {
    type: "flowers",
    list: [
      "rose",
      "tulip",
      "dandelion"
    ]
  },
  {
    type: "trees",
    list: [
      "fir",
      "pine",
      "birch"
    ]
  }
];

// Only change code below this line

var secondTree = myPlants[1].list[1];
```

</section>