React基础语法学习

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React主要有如下3个特点:

  • 作为UI(Just the UI)
  • 虚拟DOM(Virtual DOM):这是亮点 是React最重要的一个特性 放进内存 最小更新的视图,差异部分更新 diff算法
  • 数据流(Date Flow)单向数据流

学习React需要掌握哪些知识?

  • JSX语法 类似XML
  • ES6相关知识
  • 前端基础 CSS+DIV JS

例子一
(简单组件和数据传递) 使用this.props 指向自己的属性

<!DOCTYPE html> <html> <head lang="en"> <Meta charset="UTF-8"> <title>React第一个例子</title> <script type="text/javascript" src="react.js"></script> <script type="text/javascript" src="react-dom.js"></script> <script type="text/javascript" src="browser.min.js"></script> </head> <body> <div id="example"></div> <script type="text/babel"> var HelloMessage=React.createClass( { render:function(){ return <h1 style={{color:'#ff0000',fontSize:'24px'}} >Hello {this.props.name}!我是东方耀</h1>; //这是注释 React.createElement } } ); ReactDOM.render(<HelloMessage name="React 语法基础8" />,document.getElementById('example')); </script> </body> </html>

例子二(通过this.state更新视图)

<!DOCTYPE html>
<html>
<head lang="en">
    <Meta charset="UTF-8">
    <title>React第二个例子</title>
    <script type="text/javascript" src="react.js"></script>
    <script type="text/javascript" src="react-dom.js"></script>
    <script type="text/javascript" src="browser.min.js"></script>
</head>
<body>

<div id="example"></div>

<script type="text/babel"> var Timer=React.createClass( { /*初始状态*/ getInitialState:function(){ return {secondsElapsed:0}; },tick:function(){ this.setState({secondsElapsed:this.state.secondsElapsed+1}); },/*组件完成装载*/ componentDidMount:function(){ this.interval=setInterval(this.tick,1000); },/*组件将被卸载 清除定时器*/ componentWillUnmount:function(){ clearInterval(this.interval); },/*渲染视图*/ render:function(){ return( <div> Seconds Elapsed:{this.state.secondsElapsed} </div> ); } } ); React.render( <Timer />,document.getElementById('example')); </script>

</body>
</html>

例子三(简单应用)

<!DOCTYPE html> <html> <head lang="en"> <Meta charset="UTF-8"> <title>React第三个例子</title> <script type="text/javascript" src="react.js"></script> <script type="text/javascript" src="react-dom.js"></script> <script type="text/javascript" src="browser.min.js"></script> </head> <body> <div id="example"></div> <script type="text/babel"> var ShowEditor=React.createClass( { getInitialState:function(){ return {value:'你可以在这里输入文字'}; },handleChange:function(){ this.setState({value:React.findDOMNode(this.refs.textarea).value}); },render:function(){ return ( <div> <h3>输入</h3> <textarea style={{width:300,height:150,outline:'none'}} onChange={this.handleChange} ref="textarea" defaultValue={this.state.value} /> <h3>输出</h3> <div> {this.state.value} </div> </div> ); } } ); React.render(<ShowEditor />,document.getElementById('example')); </script> </body> </html>

flexBox布局

伸缩项目的属性

1.order
定义项目的排列顺序,数值越小,排列越靠前,默认值为0,语法为:order:整数值
2.flex-grow
定义伸缩项目的放大比例,默认值为0,即表示如果存在剩余空间,也不放大,语法为:flex-grow:整
数值
3.flex-shrink
定义伸缩项目的收缩能力,默认值为1 ,其语法为:flex-shrink:整数值
4.flex-basis
用来设置伸缩项目的基准值,剩余的空间按比率进行伸缩,其语法为:flex-basis:length | auto,默认
值为auto
5.flex
是flex-grow flex-shrink flex-basis这三个属性的缩写,其语法为:flex:none | flex-grow flex-shrink flexbasis,
其中第二个和第三个参数为可选参数,默认值为:0 1 auto
6.align-self
用来设置单独的伸缩项目在交叉轴上的对齐方式,会覆盖默认的对齐方式,其语法为:align-self:auto
| flex-start | flex-end | center | baseline | stretch(伸缩项目在交叉轴方向占满伸缩容器,如果交叉轴为
垂直方向的话,只有在不设置高度的情况下才能看到效果)

在React Native中使用flexBox

RN目前主要支持flexBox的如下6个属性
1.alignItems
用来定义伸缩项目在交叉轴上的对齐方式,语法为: alignItems:flex-start(默认值) | flex-end |
center | stretch
2.alignSelf
用来设置单独的伸缩项目在交叉轴上的对齐方式,会覆盖默认的对齐方式,其语法为:alignSelf:auto |
flex-start | flex-end | center | stretch(伸缩项目在交叉轴方向占满伸缩容器,如果交叉轴为垂直方向的
话,只有在不设置高度的情况下才能看到效果)
3.flex
是flex-grow flex-shrink flex-basis这三个属性的缩写,其语法为:flex:none | flex-grow flex-shrink flexbasis,
其中第二个和第三个参数为可选参数,默认值为:0 1 auto
4.flexDirection
指定主轴的方向 flex-direction:row| row-reverse | column(默认值) | column-reverse
5.flexWrap
6.justifyContent

Box实现

<!DOCTYPE html>
<html>
  <head>
    <Meta charset="utf-8">
    <title></title>
    <style> .height50 { height: 50px; } .height400 { height: 400px; } .height300 { height: 300px; } .height200 { height: 200px; } .height100 { height: 100px; } .width400 { width: 400px; } .bgred { background-color: #6AC5AC; } .bggreen { background-color: #414142; } .bgyellow { background-color: #D64078; } .Box { display: flex; flex-direction: column; flex: 1; position: relative; color: #FDC72F; line-height: 1em; } .label { top: 0; left: 0; padding: 0 3px 3px 0; position: absolute; background-color: #FDC72F; color: white; line-height: 1em; } .top { width: 100%; justify-content: center; display: flex; align-items: center; } .bottom { width: 100%; display: flex; justify-content: center; align-items: center; } .right { width: 50px; display: flex; justify-content: space-around; align-items: center; } .left { width: 50px; display: flex; justify-content: space-around; align-items: center; } .heightdashed { position: absolute; right: 20px; height: 100%; border-left: 1px solid #FDC72F; } .widthdashed { position: absolute; left: 0px; width: 100%; bottom: 24px; border-top: 1px solid #FDC72F; } .margginBox { position:absolute; top: 100px; padding-left:7px; padding-right:7px; } .borderBox { flex: 1; display: flex; justify-content: space-between; } .paddingBox { flex: 1; display: flex; justify-content: space-between; } .elementBox{ flex: 1; display: flex; justify-content: space-between; } .measureBox { flex: 1; display: flex; justify-content: flex-end; align-items: flex-end; } </style>
  </head>
  <body>
    <span class="margginBox">
      <span class="Box height400 width400">
        <span class="label">
          margin
        </span>
        <span class="top height50 bgred">
          top
        </span>
        <span class="borderBox">
          <span class="left bgred">
            left
          </span>
          <span class="Box height300 ">
            <span class="label">
              border
            </span>
            <span class="top height50 bggreen">
              top
            </span>
            <span class="paddingBox">
              <span class="left bggreen">
                left
              </span>
              <span class="Box height200 ">
                <span class="label">
                  padding
                </span>
                <span class="top height50 bgyellow">
                  top
                </span>
                <span class="elementBox">
                  <span class="left bgyellow">
                    left
                  </span>
                  <span class="Box height100 ">
                    <span class="label">
                      element
                    </span>
                    <span class="widthdashed">
                    </span>
                    <span class="heightdashed">
                    </span>
                    <span class="measureBox">
                      <span class="right">
                        height
                      </span>
                    </span>
                    <span class="bottom height50">
                      width
                    </span>
                  </span>
                  <span class="right bgyellow">
                    right
                  </span>
                </span>
                <span class="bottom height50 bgyellow">
                  bottom
                </span>
              </span>
              <span class="right bggreen">
                right
              </span>
            </span>
            <span class="bottom height50 bggreen">
              bottom
            </span>
          </span>
          <span class="right bgred">
            right
          </span>
        </span>
        <span class="bottom height50 bgred">
          bottom
        </span>
      </span>
    </span>
  </body>
</html>

效果如下

ReactNative版实现

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 */
'use strict';
import React,{
  AppRegistry,Component,StyleSheet,Text,View
} from 'react-native';

class DongFang extends Component {
  render() {
    return (
        <View style={[BoxStyles.margginBox]} ref="lab1">
          <View style={[BoxStyles.Box,BoxStyles.height400,BoxStyles.width400]}>
            <View style={[BoxStyles.top,BoxStyles.height50,BoxStyles.bgred]}>
              <Text style={BoxStyles.yellow}>top</Text></View>
            <View style={[BoxStyles.borderBox]}>
              <View style={[BoxStyles.left,BoxStyles.bgred]} >
                <Text style={BoxStyles.yellow}>left</Text></View>
              <View style={[BoxStyles.Box,BoxStyles.height300]}>
                <View style={[BoxStyles.top,BoxStyles.bggreen]}>
                  <Text style={BoxStyles.yellow}>top</Text></View>
                <View style={[BoxStyles.paddingBox]}>
                  <View style={[BoxStyles.left,BoxStyles.bggreen]} >
                    <Text style={BoxStyles.yellow}>left</Text></View>
                  <View style={[BoxStyles.Box,BoxStyles.height200]}>
                    <View style={[BoxStyles.top,BoxStyles.bgyellow]}>
                      <Text style={BoxStyles.yellow}>top</Text></View>
                    <View style={[BoxStyles.elementBox]}>
                      <View style={[BoxStyles.left,BoxStyles.bgyellow]} >
                        <Text style={BoxStyles.yellow}>left</Text></View>
                      <View style={[BoxStyles.Box,BoxStyles.height100]}>
                        <View style={[BoxStyles.label]}>
                          <Text style={BoxStyles.white}>element</Text></View>
                        <View style={[BoxStyles.widthdashed]} ></View>
                        <View style={[BoxStyles.heightdashed]} ></View>
                        <View style={[BoxStyles.measureBox]} >
                          <View style={[BoxStyles.right]}>
                            <Text style={[BoxStyles.yellow]}>height</Text></View>
                        </View>
                        <View style={[BoxStyles.bottom,BoxStyles.height50]}>
                          <Text style={BoxStyles.yellow}>width</Text></View>
                      </View>
                      <View style={[BoxStyles.right,BoxStyles.bgyellow]}><Text style={BoxStyles.yellow}>right</Text></View>
                    </View>
                    <View style={[BoxStyles.bottom,BoxStyles.bgyellow]}>
                      <Text style={BoxStyles.yellow}>bottom</Text></View>
                    <View style={[BoxStyles.label]}>
                      <Text style={BoxStyles.white}>padding</Text></View>
                  </View>
                  <View style={[BoxStyles.right,BoxStyles.bggreen]}><Text style={BoxStyles.yellow}>right</Text></View>
                </View>
                <View style={[BoxStyles.bottom,BoxStyles.bggreen]}>
                  <Text style={BoxStyles.yellow}>bottom</Text></View>
                <View style={[BoxStyles.label]}><Text style={BoxStyles.white}>border</Text></View>
              </View>
              <View style={[BoxStyles.right,BoxStyles.bgred]}>
                <Text style={BoxStyles.yellow}>right</Text></View>
            </View>
            <View style={[BoxStyles.bottom,BoxStyles.bgred]}>
              <Text style={BoxStyles.yellow}>bottom</Text></View>
            <View style={[BoxStyles.label]} ><Text style={BoxStyles.white}>margin</Text></View>
          </View>
        </View>
    );
  }
}

const BoxStyles = StyleSheet.create({
  height50:{
    height: 50,},height400:{
    height: 400,height300:{
    height: 300,height200:{
    height: 200,height100:{
    height: 100,width400:{
    width: 400,width300:{
    width: 300,width200:{
    width: 200,width100:{
    width: 100,bgred: {
    backgroundColor:'#6AC5AC',bggreen: {
    backgroundColor: '#414142',bgyellow: {
    backgroundColor: '#D64078',Box: {
    flexDirection: 'column',flex: 1,position: 'relative',label: {
    top: 0,left: 0,paddingTop: 0,paddingRight: 3,paddingBottom: 3,paddingLeft: 0,position: 'absolute',backgroundColor: '#FDC72F',top: {
    justifyContent: 'center',alignItems: 'center',bottom: {
    justifyContent: 'center',right: {
    width: 50,justifyContent: 'space-around',left: {
    width: 50,heightdashed: {
    bottom: 0,top: 0,right: 20,borderLeftWidth: 1,borderLeftColor: '#FDC72F',widthdashed: {
    bottom: 25,right: 0,borderTopWidth: 1,borderTopColor: '#FDC72F',yellow: {
    color: '#FDC72F',fontWeight:'900',white: {
    color: 'white',margginBox:{
    position: 'absolute',top: 100,paddingLeft:7,paddingRight:7,borderBox:{
    flex: 1,justifyContent: 'space-between',flexDirection: 'row',paddingBox:{
    flex: 1,elementBox:{
    flex: 1,measureBox:{
    flex: 1,justifyContent: 'flex-end',alignItems:'flex-end',container: {
    flex: 1,justifyContent: 'center',backgroundColor: '#F5FCFF',welcome: {
    fontSize: 20,textAlign: 'center',margin: 10,instructions: {
    textAlign: 'center',color: '#333333',marginBottom: 5,});

AppRegistry.registerComponent('DongFang',() => DongFang);
原文链接:https://www.f2er.com/react/306565.html

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