Detailed explanation of component definition and usage in React
This time I will bring you a detailed explanation of the use of component definitions in React. What are the precautions for the use of component definitions in React. The following is a practical case, let's take a look.
Components
Components allow you to divide the UI into independent, reusable widgets, and design each widget individually.
Plays an important role in single page applications (SPA)
Simple implementation of components - functional components
import React from 'react' import ReactDOM from 'react-dom' let Component1 = () => { return <h1>React Component</h1> } ReactDOM.render( <Component1 />, document.getElementById('app') )
Class components-ES5 syntax
var React = require('react'); var ReactDOM = require('react-dom') var Component1 = React.createClass({ render: function(){ return ( <p> <h1>Tom</h1> <h1>Sam</h1> </p> ) } }) ReactDOM.render( <Component1 />, document.getElementById('app') )
Class component - ES6 syntax
import React from 'react' import ReactDOM from 'react-dom' class Component1 extends React.Component{ render(){ return ( <p> <h1>Tom</h1> <h1>Sam</h1> </p> ) } } ReactDOM.render( <Component1 />, document.getElementById('app') )
Effect preview
Component summary
The first letter of the component name must be capitalized
The function returns a virtual DOM node
Class components must have a render method
render must return a virtual DOM node
In actual work, class components are a commonly used method
Component properties (Props)
Because the call of the component is In the form of html tags, and html tags can add attributes, so custom attributes can also be added to React components, and the attributes are obtained using the this.props
function Component
import React from 'react' import ReactDOM from 'react-dom' let Component1 = (props) => { return <h1>name-{props.name}</h1> } ReactDOM.render( <Component1 name="Sam"/>, document.getElementById('app') )
Class component
import React from 'react' import ReactDOM from 'react-dom' class Component1 extends React.Component{ render(){ return <h1>name-{this.props.name}</h1> } } ReactDOM.render( <Component1 name="Sam"/>, document.getElementById('app') )
DefaultProps
In addition to passing values in the form of DOM node attributes when calling, the properties of components can also be set to default If the corresponding attribute value is not passed when calling, the default attribute value will be used. getDefalutProps
This method will only be called once.
//es5 var React = require('react'); var ReactDOM = require('react-dom'); var Component1 = React.createClass({ getDefaultProps: function(){ return { name: 'Tom', age: 20 } }, render: function(){ return ( <p> <p>姓名:{this.props.name}</p> <p>年龄:{this.props.age}</p> </p> ) } }) //es6 import React from 'react'; import ReactDOM from 'react-dom'; class Component1 extends React.Component{ static defaultProps = { name: 'Tom', age: 20 } render(){ return ( <p> <h1>姓名:{this.props.name}</h1> <h1>年龄:{this.props.age}</h1> </p> ) } } //或者 Component1.defaultProps = { name: "Sam", age: 22 } //使用 ReactDOM.render(<Component1/>, document.getElementById('p1'));
Attribute type rules (propTypes)
Normally, when defining a component, the attributes are defined and some usage conditions are added, such as certain attribute values. Data type must be an array, or some properties cannot be empty. At this time, they can be set through propTypes
.
import React from 'react'; import ReactDOM from 'react-dom'; import PropTypes from 'prop-types' class Component1 extends React.Component{ render(){ return ( <p> <p>姓名:{this.props.name}</p> <p>年龄:{this.props.age}</p> <p>学科:</p> <ul> { this.props.subjects.map(function(_item){ return <li>{_item}</li> }) } </ul> </p> ) } } //定义属性 name 为字符串且必须有值 Component1.propTypes = { name: PropTypes.string } ReactDOM.render(<Component1 name="Tom"/>, document.getElementById('p1'));
prop is optional by default, commonly used types:
PropTypes.array
PropTypes.bool
PropTypes.func
PropTypes.number
PropTypes.object
##PropTypes.string
PropTypes.symbol
PropTypes.any.isRequired
import React from 'react'
import ReactDOM from 'react-dom'
let Component1 = () => {
return <h1>React Component</h1>
}
ReactDOM.render(
<Component1 />,
document.getElementById('app')
)
Copy after loginCopy after login
Class components-ES5 syntaximport React from 'react' import ReactDOM from 'react-dom' let Component1 = () => { return <h1>React Component</h1> } ReactDOM.render( <Component1 />, document.getElementById('app') )
var React = require('react');
var ReactDOM = require('react-dom')
var Component1 = React.createClass({
render: function(){
return (
<p>
<h1>Tom</h1>
<h1>Sam</h1>
</p>
)
}
})
ReactDOM.render(
<Component1 />,
document.getElementById('app')
)
Copy after loginCopy after login
Class component - ES6 syntaxvar React = require('react'); var ReactDOM = require('react-dom') var Component1 = React.createClass({ render: function(){ return ( <p> <h1>Tom</h1> <h1>Sam</h1> </p> ) } }) ReactDOM.render( <Component1 />, document.getElementById('app') )
import React from 'react'
import ReactDOM from 'react-dom'
class Component1 extends React.Component{
render(){
return (
<p>
<h1>Tom</h1>
<h1>Sam</h1>
</p>
)
}
}
ReactDOM.render(
<Component1 />,
document.getElementById('app')
)
Copy after loginCopy after login
Effect previewComponent summary
import React from 'react' import ReactDOM from 'react-dom' class Component1 extends React.Component{ render(){ return ( <p> <h1>Tom</h1> <h1>Sam</h1> </p> ) } } ReactDOM.render( <Component1 />, document.getElementById('app') )
- The first letter of the component name must be capitalized
- The function returns a virtual DOM node
- Class components must have a render method
- render must return a virtual DOM node
- In actual work, class components are a commonly used method
this.props
import React from 'react'
import ReactDOM from 'react-dom'
let Component1 = (props) => {
return <h1>name-{props.name}</h1>
}
ReactDOM.render(
<Component1 name="Sam"/>,
document.getElementById('app')
)
Copy after loginCopy after login
Class componentimport React from 'react' import ReactDOM from 'react-dom' let Component1 = (props) => { return <h1>name-{props.name}</h1> } ReactDOM.render( <Component1 name="Sam"/>, document.getElementById('app') )
import React from 'react'
import ReactDOM from 'react-dom'
class Component1 extends React.Component{
render(){
return <h1>name-{this.props.name}</h1>
}
}
ReactDOM.render(
<Component1 name="Sam"/>,
document.getElementById('app')
)
Copy after loginCopy after login
DefaultPropsIn addition to passing values in the form of DOM node attributes when calling, the properties of components can also be set to default If the corresponding attribute value is not passed when calling, the default attribute value will be used. import React from 'react' import ReactDOM from 'react-dom' class Component1 extends React.Component{ render(){ return <h1>name-{this.props.name}</h1> } } ReactDOM.render( <Component1 name="Sam"/>, document.getElementById('app') )
getDefalutProps This method will only be called once.
//es5 var React = require('react'); var ReactDOM = require('react-dom'); var Component1 = React.createClass({ getDefaultProps: function(){ return { name: 'Tom', age: 20 } }, render: function(){ return ( <p> <p>姓名:{this.props.name}</p> <p>年龄:{this.props.age}</p> </p> ) } }) //es6 import React from 'react'; import ReactDOM from 'react-dom'; class Component1 extends React.Component{ static defaultProps = { name: 'Tom', age: 20 } render(){ return ( <p> <h1>姓名:{this.props.name}</h1> <h1>年龄:{this.props.age}</h1> </p> ) } } //或者 Component1.defaultProps = { name: "Sam", age: 22 } //使用 ReactDOM.render(<Component1/>, document.getElementById('p1'));
属性的类型规则(propTypes)
通常情况下,在定义一个组件的时候把属性定义好,会加上一些使用的条件限制,比如某些属性值的数据类型必须是数组,或者某些属性不能为空,在这个时候,可以通过 propTypes
来设置。
import React from 'react'; import ReactDOM from 'react-dom'; import PropTypes from 'prop-types' class Component1 extends React.Component{ render(){ return ( <p> <p>姓名:{this.props.name}</p> <p>年龄:{this.props.age}</p> <p>学科:</p> <ul> { this.props.subjects.map(function(_item){ return <li>{_item}</li> }) } </ul> </p> ) } } //定义属性 name 为字符串且必须有值 Component1.propTypes = { name: PropTypes.string } ReactDOM.render(<Component1 name="Tom"/>, document.getElementById('p1'));
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