When you are using React components you need to be able to access specific references to individual components. This is done by defining a ref . ! DOCTYPE html html head lang ="en" meta charset ="UTF-8" title React Lesson 5: Using Refs to
When you are using React components you need to be able to access specific references to individual components. This is done by defining a ref
.
<span><span>DOCTYPE html</span><span>></span> <span><span>html</span><span>></span> <span><span>head </span><span>lang</span><span>="en"</span><span>></span> <span><span>meta </span><span>charset</span><span>="UTF-8"</span><span>></span> <span><span>title</span><span>></span>React Lesson 5: Using Refs to Access Components<span></span><span>title</span><span>></span> <span></span><span>head</span><span>></span> <span><span>body</span><span>></span> <span><span>script </span><span>src</span><span>="https://cdnjs.cloudflare.com/ajax/libs/react/0.12.2/react.js"</span><span>></span><span>script</span><span>></span> <span><span>script </span><span>src</span><span>="https://cdnjs.cloudflare.com/ajax/libs/react/0.12.2/JSXTransformer.js"</span><span>></span><span>script</span><span>></span> <span><span>script </span><span>type</span><span>="text/jsx"</span><span>></span> <span>var</span><span> React_app </span><span>=</span><span> React.createClass({ getInitialState: </span><span>function</span><span>() { </span><span>return</span><span> { red: </span><span>128</span><span>, green: </span><span>128</span><span>, blue: </span><span>128</span><span> } }, myUpdate: </span><span>function</span><span>(){ </span><span>this</span><span>.setState({ red: </span><span>this</span><span>.refs.red.getDOMNode().value, green: </span><span>this</span><span>.refs.green.getDOMNode().value, blue: </span><span>this</span><span>.refs.blue.getDOMNode().value }); }, render: </span><span>function</span><span>() { </span><span>return</span><span> ( </span><span><span>div</span><span>></span> <span><span>Silder update</span><span>=</span><span>{</span><span>this</span><span>.myUpdate} ref</span><span>=</span><span>"</span><span>red</span><span>"</span><span>><span>/</span><span>Silder><label>{this.state.red}<span>/</span><span>label</span><span>><span>br</span><span>/</span><span>></span> <span><span>Silder update</span><span>=</span><span>{</span><span>this</span><span>.myUpdate} ref</span><span>=</span><span>"</span><span>green</span><span>"</span><span>><span>/</span><span>Silder><label>{this.state.green}<span>/</span><span>label</span><span>><span>br</span><span>/</span><span>></span> <span><span>Silder update</span><span>=</span><span>{</span><span>this</span><span>.myUpdate} ref</span><span>=</span><span>"</span><span>blue</span><span>"</span><span>><span>/</span><span>Silder><label>{this.state.blue}<span>/</span><span>label</span><span>><span>br</span><span>/</span><span>></span> <span><span>/</span><span>div></span> <span> ); } }); </span><span>var</span><span> Silder </span><span>=</span><span> React.createClass({ render: </span><span>function</span><span>(){ </span><span>return</span><span> ( </span><span><span>input type</span><span>=</span><span>"</span><span>range</span><span>"</span><span> min</span><span>=</span><span>"</span><span>0</span><span>"</span><span> max</span><span>=</span><span>"</span><span>255</span><span>"</span><span> onChange</span><span>=</span><span>{</span><span>this</span><span>.props.update}</span><span>/</span><span>></span> <span> ) } }); React.render(</span><span><span>React_app </span><span>/</span><span>>, document.body);</span> <span></span><span>script</span><span>></span> <span></span><span>body</span><span>></span> <span></span><span>html</span><span>></span></span></span></span></span></label></span></span></span></span></label></span></span></span></span></label></span></span></span></span></span></span></span></span></span></span></span></span></span>
Here we use getDOMNode() to get the html node:
<span><span>Silder </span><span>update</span><span>={this.myUpdate} </span><span>ref</span><span>="red"</span><span>></span><span>Silder</span><span>></span></span>
then get value from it:
this.refs.red.getDOMNode().value
But, if we add a div:
<span> var Silder = React.createClass({ render: function(){ return ( </span><span><span>div</span><span>></span> <span><!--</span><span> added </span><span>--></span> <span><span>input </span><span>type</span><span>="range"</span><span> min</span><span>="0"</span><span> max</span><span>="255"</span><span> onChange</span><span>={this.props.update}</span><span>/></span> <span></span><span>div</span><span>></span> <span><!--</span><span> added </span><span>--></span><span> ) } });</span></span></span>
We found it doesn't work.
The way can solve this problem is by adding another ref to the input element:
<span> var Silder = React.createClass({ render: function(){ return ( </span><span><span>div </span><span>></span> <span><span>input </span><span>type</span><span>="range"</span><span> min</span><span>="0"</span><span> max</span><span>="255"</span><span> ref</span><span>="range"</span><span> onChange</span><span>={this.props.update}</span><span>/></span> <span></span><span>div</span><span>></span><span> ) } });</span></span></span>
myUpdate: <span>function</span><span>(){ </span><span>this</span><span>.setState({ red: </span><span>this</span><span>.refs.red.refs.range.getDOMNode().value, green: </span><span>this</span><span>.refs.green.refs.range.getDOMNode().value, blue: </span><span>this</span><span>.refs.blue.refs.range.getDOMNode().value }); },</span>

在react中,canvas用于绘制各种图表、动画等;可以利用“react-konva”插件使用canvas,该插件是一个canvas第三方库,用于使用React操作canvas绘制复杂的画布图形,并提供了元素的事件机制和拖放操作的支持。

在react中,antd是基于Ant Design的React UI组件库,主要用于研发企业级中后台产品;dva是一个基于redux和“redux-saga”的数据流方案,内置了“react-router”和fetch,可理解为应用框架。

React不是双向数据流,而是单向数据流。单向数据流是指数据在某个节点被改动后,只会影响一个方向上的其他节点;React中的表现就是数据主要通过props从父节点传递到子节点,若父级的某个props改变了,React会重渲染所有子节点。

因为在react中需要利用到webpack,而webpack依赖nodejs;webpack是一个模块打包机,在执行打包压缩的时候是依赖nodejs的,没有nodejs就不能使用webpack,所以react需要使用nodejs。

在react中,forceupdate()用于强制使组件跳过shouldComponentUpdate(),直接调用render(),可以触发组件的正常生命周期方法,语法为“component.forceUpdate(callback)”。

react是组件化开发;组件化是React的核心思想,可以开发出一个个独立可复用的小组件来构造应用,任何的应用都会被抽象成一颗组件树,组件化开发也就是将一个页面拆分成一个个小的功能模块,每个功能完成自己这部分独立功能。

react与vue的虚拟dom没有区别;react和vue的虚拟dom都是用js对象来模拟真实DOM,用虚拟DOM的diff来最小化更新真实DOM,可以减小不必要的性能损耗,按颗粒度分为不同的类型比较同层级dom节点,进行增、删、移的操作。

react和reactdom的区别是:ReactDom只做和浏览器或DOM相关的操作,例如“ReactDOM.findDOMNode()”操作;而react负责除浏览器和DOM以外的相关操作,ReactDom是React的一部分。


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