[React] Stop Memory Leaks with componentWillUnmount Lifecycle Method in React
In this lesson we'll take a stopwatch component we built in another lesson and identify and fix a memory leak.
<body>
<script src="https://unpkg.com/react@16.0.0/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16.0.0/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone@6.26.0/babel.js"></script>
<div id="root"></div> <script type="text/babel">
class StopWatch extends React.Component {
state = {lapse: 0, running: false}
handleRunClick = () => {
this.setState(state => {
if (state.running) {
clearInterval(this.timer)
} else {
const startTime =
Date.now() - this.state.lapse
this.timer = setInterval(() => {
this.setState(
{
lapse: Date.now() - startTime,
},
() => {
console.log(this.state.lapse)
},
)
})
}
return {running: !state.running}
})
}
handleClearClick = () => {
clearInterval(this.timer)
this.setState({lapse: 0, running: false})
}
componentWillUnmount() {
clearInterval(this.timer)
}
render() {
const {lapse, running} = this.state
const buttonStyles = {
border: '1px solid #ccc',
background: '#fff',
fontSize: '2em',
padding: 15,
margin: 5,
width: 200,
}
return (
<div style={{textAlign: 'center'}}>
<label
style={{
fontSize: '5em',
display: 'block',
}}
>
{lapse}ms
</label>
<button
onClick={this.handleRunClick}
style={buttonStyles}
>
{running ? 'Stop' : 'Start'}
</button>
<button
onClick={this.handleClearClick}
style={buttonStyles}
>
Clear
</button>
</div>
)
}
} class App extends React.Component {
state = {showStopWatch: true}
render() {
const {showStopWatch} = this.state
return (
<div>
<label>
Show Stop Watch{' '}
<input
type="checkbox"
checked={showStopWatch}
onChange={() =>
this.setState(s => ({
showStopWatch: !s.showStopWatch,
}))}
/>
</label>
<hr />
{showStopWatch ? <StopWatch /> : null}
</div>
)
}
} const element = <App />
ReactDOM.render(
element,
document.getElementById('root'),
)
</script>
</body>
Tow things to notice here is that:
1. this.setState(), we can pass an update function, which take param 'state' and return a new state
this.setState((state) => ({newState}))
2. Pass a second param to setState() as a callback:
this.setState(newState, callback)
[React] Stop Memory Leaks with componentWillUnmount Lifecycle Method in React的更多相关文章
- The Introduction of Java Memory Leaks
One of the most significant advantages of Java is its memory management. You simply create objects a ...
- On Memory Leaks in Java and in Android.
from:http://chaosinmotion.com/blog/?p=696 Just because it's a garbage collected language doesn't mea ...
- Activitys, Threads, & Memory Leaks
Activitys, Threads, & Memory Leaks 在Android编程中,一个公认的难题是在Activity的生命周期如何协调长期运行的任务和避免有可能出现的内存泄漏问题. ...
- [转]Activitys, Threads, & Memory Leaks
转自:http://www.androiddesignpatterns.com/2013/04/activitys-threads-memory-leaks.html http://www.cnblo ...
- Instruments Tutorial for iOS: How To Debug Memory Leaks【转】
If you're new here, you may want to subscribe to my RSS feed or follow me on Twitter. Thanks for vis ...
- Instruments Tutorial for iOS: How To Debug Memory Leaks
http://www.raywenderlich.com/2696/instruments-tutorial-for-ios-how-to-debug-memory-leaks Update 4/12 ...
- Find out when memory leaks are a concern and how to prevent them
Handling memory leaks in Java programs Find out when memory leaks are a concern and how to prevent t ...
- Avoiding memory leaks
Android applications are, at least on the T-Mobile G1, limited to 16 MB of heap. It's both a lot of ...
- Identify Memory Leaks in Visual CPP Applications —— VLD内存泄漏检测工具
原文地址:http://www.codeproject.com/Articles/1045847/Identify-Memory-Leaks-in-Visual-CPP-Applications 基于 ...
随机推荐
- Data Member Order
https://docs.microsoft.com/en-us/dotnet/framework/wcf/feature-details/data-member-order In some appl ...
- BsonDocument
http://api.mongodb.com/csharp/current/html/T_MongoDB_Bson_BsonDocument.htm 如何取出document中的数据 BsonDocu ...
- Excel操作之VLOOKUP
https://support.office.com/en-us/article/VLOOKUP-function-0bbc8083-26fe-4963-8ab8-93a18ad188a1 Use V ...
- 【转】dig详解
[root@localhost ~]# dig www.a.com ; <<>> DiG 9.2.4 <<>> www.a.com ;; global ...
- git的学习笔记整理
Git学习较好的网址:http://www.liaoxuefeng.com/wiki/0013739516305929606dd18361248578c67b8067c8c017b000/001373 ...
- 4.Mocha的基本用法
转自:http://www.ruanyifeng.com/blog/2015/12/a-mocha-tutorial-of-examples.html 有了测试脚本以后,就可以用Mocha运行它.请进 ...
- 2.LINUX常用命令
Linux 必备指令摘要一般用户指令/bin 指令 功能说明 范例 bash GNU Bouren-Again Shell bash shell_script cat 观看一般文本文件 cat fil ...
- JavaScript,ES5和ES6的区别
什么是JavaScript JavaScript一种动态类型.弱类型.基于原型的客户端脚本语言,用来给HTML网页增加动态功能.(好吧,概念什么最讨厌了) 动态: 在运行时确定数据类型.变量使用之前不 ...
- 八 ROI（region of interest）和泛洪填充
一.ROI 感兴趣区(Region of Interest,ROIs) 是图像的一部分,它通过在图像上选择或使用诸如设定阈值(thresholding) 或者从其他文件(如矢量> 转换获得等方法 ...
- Vue总结（二）
原始引用:开发时使用开发版本,线上使用生产版本. 原始引用到html中,在浏览器中控制台输入Vue,输出一个函数就可以. defineProperties实现的数据绑定. //defineProper ...