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What can the react framework do? Detailed introduction to react framework (with complete usage examples)

寻∝梦Original: 2018-09-11 16:45:1712430browse

React is a JavaScript framework for building "predictable" and "declarative" web user interfaces, which has enabled Facebook to develop web applications faster. Let’s take a look at the content of the article

1. Features:

1. Simply describe your application at any point in time What it should look like is that React will automatically manage UI updates when the data changes.

2. Declarative When the data changes, React is conceptually the same as clicking F5. In fact, it only updates part of the change. React is about building reusable components. In fact, with React all you do is build components. Encapsulation makes component code reuse, testing, and separation of concerns easier.

In addition, there are the following points to note:

React is not an MVC framework

React does not use templates

Responsive update is very simple

2. Main principles

In traditional web applications, operating DOM is generally Direct update operation, but we know that DOM updates are usually expensive. In order to reduce operations on the DOM as much as possible, React provides a different and powerful way to update the DOM instead of direct DOM operations. It is Virtual DOM, a lightweight virtual DOM, which is an object abstracted by React, describing what the dom should look like and how it should be presented. The real DOM is updated through this Virtual DOM, and this Virtual DOM manages the update of the real DOM.

Why can it be faster through this extra layer of Virtual DOM operations? This is because React has a diff algorithm. Updating the Virtual DOM does not guarantee that it will affect the real DOM immediately. React will wait until the event loop ends, and then use this diff algorithm to calculate the smallest value by comparing the current new dom representation with the previous one. Steps to update the real DOM.

Components Components

Nodes in the DOM tree are called elements, but here it is different, Virtual DOM It is called commponent. The node of Virtual DOM is a complete abstract component, which is composed of commponents.

Note: The use of components is extremely important in React, because the existence of components makes calculating DOM diff more efficient.

State and Render

How does React present the real DOM, how to render components, when to render, and how to update synchronously. This requires a brief understanding of State and Render. Rendered. The state attribute contains some data needed to define the component. When the data changes, Render will be called to re-render. Here, the data can only be updated through the provided setState method.

Let’s take a look at the official website demo first:

<!DOCTYPE html>
<html>
<head>
<script src="http://fb.me/react-0.12.1.js"></script>
<script src="http://fb.me/JSXTransformer-0.12.1.js"></script>
</head>
<body>
<p id="example"></p>
<script type="text/jsx">
React.render(
<h1>Hello, world!</h1>,
document.getElementById(&#39;example&#39;)
);
</script>
</body>
</html>

is very simple. When accessed by a browser, you can see the words Hello, world!. JSXTransformer.js supports parsing JSX syntax. JSX is a syntax that can write html code in Javascript. If you don't like it, React also provides native Javascript methods. (If you want to see more, go to the PHP Chinese website React Reference Manual column to learn)

Another demo:

<html>
<head>
<title>Hello React</title>
<script src="http://fb.me/react-0.12.1.js"></script>
<script src="http://fb.me/JSXTransformer-0.12.1.js"></script>
<script src="http://code.jquery.com/jquery-1.10.0.min.js"></script>
<script src="http://cdnjs.cloudflare.com/ajax/libs/showdown/0.3.1/showdown.min.js"></script>
<style>
#content{
width: 800px;
margin: 0 auto;
padding: 5px 10px;
background-color:#eee;
}
.commentBox h1{
background-color: #bbb;
}
.commentList{
border: 1px solid yellow;
padding:10px;
}
.commentList .comment{
border: 1px solid #bbb;
padding-left: 10px;
margin-bottom:10px;
}
.commentList .commentAuthor{
font-size: 20px;
}
.commentForm{
margin-top: 20px;
border: 1px solid red;
padding:10px;
}
.commentForm textarea{
width:100%;
height:50px;
margin:10px 0 10px 2px;
}
</style>
</head>
<body>
<p id="content"></p>
<script type="text/jsx">
var staticData = [
{author: "张飞", text: "我在写一条评论~！"},
{author: "关羽", text: "2货，都知道你在写的是一条评论。。"},
{author: "刘备", text: "哎，咋跟这俩逗逼结拜了！"}
];
var converter = new Showdown.converter();//markdown
/** 组件结构：
<CommentBox>
<CommentList>
<Comment />
</CommentList>
<CommentForm />
</CommentBox>
*/
//评论内容组件
var Comment = React.createClass({
render: function (){
var rawMarkup = converter.makeHtml(this.props.children.toString());
return (
<p className="comment">
<h2 className="commentAuthor">
{this.props.author}:
</h2>
<span dangerouslySetInnerHTML={{__html: rawMarkup}} />
</p>
);
}
});
//评论列表组件
var CommentList = React.createClass({
render: function (){
var commentNodes = this.props.data.map(function (comment){
return (
<Comment author={comment.author}>
{comment.text}
</Comment>
);
});
return (
<p className="commentList">
{commentNodes}
</p>
);
}
});
//评论表单组件
var CommentForm = React.createClass({
handleSubmit: function (e){
e.preventDefault();
var author = this.refs.author.getDOMNode().value.trim();
var text = this.refs.text.getDOMNode().value.trim();
if(!author || !text){
return;
}
this.props.onCommentSubmit({author: author, text: text});
this.refs.author.getDOMNode().value = &#39;&#39;;
this.refs.text.getDOMNode().value = &#39;&#39;;
return;
},
render: function (){
return (
<form className="commentForm" onSubmit={this.handleSubmit}>
<input type="text" placeholder="Your name" ref="author" /><br/>
<textarea type="text" placeholder="Say something..." ref="text" ></textarea><br/>
<input type="submit" value="Post" />
</form>
);
}
});
//评论块组件
var CommentBox = React.createClass({
loadCommentsFromServer: function (){
this.setState({data: staticData});
/*

For the sake of convenience, I will not go here Server-side, you can try it yourself

$.ajax({
url: this.props.url + "?_t=" + new Date().valueOf(),
dataType: &#39;json&#39;,
success: function (data){
this.setState({data: data});
}.bind(this),
error: function (xhr, status, err){
console.error(this.props.url, status, err.toString());
}.bind(this)
});
*/
},
handleCommentSubmit: function (comment){
//TODO: submit to the server and refresh the list
var comments = this.state.data;
var newComments = comments.concat([comment]);
//这里也不向后端提交了
staticData = newComments;
this.setState({data: newComments});
},
//初始化 相当于构造函数
getInitialState: function (){
return {data: []};
},
//组件添加的时候运行
componentDidMount: function (){
this.loadCommentsFromServer();
this.interval = setInterval(this.loadCommentsFromServer, this.props.pollInterval);
},
//组件删除的时候运行
componentWillUnmount: function() {
clearInterval(this.interval);
},
//调用setState或者父级组件重新渲染不同的props时才会重新调用
render: function (){
return (
<p className="commentBox">
<h1>Comments</h1>
<CommentList data={this.state.data}/>
<CommentForm onCommentSubmit={this.handleCommentSubmit} />
</p>
);
}
});
//当前目录需要有comments.json文件
//这里定义属性，如url、pollInterval，包含在props属性中
React.render(
<CommentBox url="comments.json" pollInterval="2000" />,
document.getElementById("content")
);
</script>
</body>
</html>

Effect:

What can the react framework do? Detailed introduction to react framework (with complete usage examples)

This article ends here (if you want to see more, go to the PHP Chinese websiteReact User Manual column), if you have any questions, you can leave a message below.

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