freeCodeCamp/curriculum/challenges/chinese/04-data-visualization/data-visualization-with-d3/dynamically-change-the-heig...

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---
id: 587d7fa9367417b2b2512bcf
title: Dynamically Change the Height of Each Bar
required:
- src: 'https://cdnjs.cloudflare.com/ajax/libs/d3/4.3.0/d3.min.js'
challengeType: 6
videoUrl: ''
localeTitle: 动态改变每个栏的高度
---
## Description
<section id="description">每个条的高度可以设置为数组中数据点的值,类似于动态设置<code>x</code>值的方式。 <blockquote> selection.attr“property”di=&gt; { <br> / * <br> * d是数据点值<br> * i是数组中数据点的索引<br> * / <br> } </blockquote></section>
## Instructions
<section id="instructions">更改<code>height</code>属性的回调函数以返回数据值乘以3. <strong>注意</strong> <br>请记住,将所有数据点乘以相同的常量可以缩放数据(如放大)。在此示例中,有助于查看条形值之间的差异。 </section>
## Tests
<section id='tests'>
```yml
tests:
- text: 第一个<code>rect</code>的<code>height</code>应为36。
testString: 'assert($("rect").eq(0).attr("height") == "36", "The first <code>rect</code> should have a <code>height</code> of 36.");'
- text: 第二个<code>rect</code>的<code>height</code>应为93。
testString: 'assert($("rect").eq(1).attr("height") == "93", "The second <code>rect</code> should have a <code>height</code> of 93.");'
- text: 第三个<code>rect</code>的<code>height</code>应为66。
testString: 'assert($("rect").eq(2).attr("height") == "66", "The third <code>rect</code> should have a <code>height</code> of 66.");'
- text: 第四个<code>rect</code>的<code>height</code>应为51。
testString: 'assert($("rect").eq(3).attr("height") == "51", "The fourth <code>rect</code> should have a <code>height</code> of 51.");'
- text: 第五个<code>rect</code>的<code>height</code>应为75。
testString: 'assert($("rect").eq(4).attr("height") == "75", "The fifth <code>rect</code> should have a <code>height</code> of 75.");'
- text: 第六个<code>rect</code>的<code>height</code>应为54。
testString: 'assert($("rect").eq(5).attr("height") == "54", "The sixth <code>rect</code> should have a <code>height</code> of 54.");'
- text: 第七个<code>rect</code>的<code>height</code>应为87。
testString: 'assert($("rect").eq(6).attr("height") == "87", "The seventh <code>rect</code> should have a <code>height</code> of 87.");'
- text: 第八个<code>rect</code>应该有42的<code>height</code> 。
testString: 'assert($("rect").eq(7).attr("height") == "42", "The eighth <code>rect</code> should have a <code>height</code> of 42.");'
- text: 第九个<code>rect</code>的<code>height</code>应为27。
testString: 'assert($("rect").eq(8).attr("height") == "27", "The ninth <code>rect</code> should have a <code>height</code> of 27.");'
```
</section>
## Challenge Seed
<section id='challengeSeed'>
<div id='html-seed'>
```html
<body>
<script>
const dataset = [12, 31, 22, 17, 25, 18, 29, 14, 9];
const w = 500;
const h = 100;
const svg = d3.select("body")
.append("svg")
.attr("width", w)
.attr("height", h);
svg.selectAll("rect")
.data(dataset)
.enter()
.append("rect")
.attr("x", (d, i) => i * 30)
.attr("y", 0)
.attr("width", 25)
.attr("height", (d, i) => {
// Add your code below this line
// Add your code above this line
});
</script>
</body>
```
</div>
</section>
## Solution
<section id='solution'>
```js
// solution required
```
</section>