React入門10-react組件優化

 

1. 在shouldComponentUpdate聲明週期中， 自己處理邏輯

import React, { Component } from 'react'

class Comment extends Component {
    shouldComponentUpdate({data: {name, score}}) {
        if (name === this.props.data.name && score === this.props.data.score) {
            return false
        }
        
        return true
    }
    render() {
        console.log('-----render!---------')
        return (
            <div>
                <p>{this.props.data.name}</p>
                <p>{this.props.data.score}</p>
            </div>
        )
    }
}


export default class CommentList extends Component {
    constructor(props) {
        super(props)
        this.state = {
            commentList: []
        }
    }

    componentDidMount() {
        setInterval(() => {
            this.setState({
                commentList: [
                    {name: 'zhangsan', score: '99'},
                    {name: 'lisi', score: '100'}
                ]
            })
        }, 1000)
    }
    render() {
        return (
            <div>
                {this.state.commentList.map((item, index) => <Comment key={index} data= {item}/>)}
            </div>
        )
    }
}

2. pureComponent(淺比較, 此時屬性展開)

import React, { Component } from 'react'
class Comment extends React.PureComponent {
    render() {
        console.log('-----render!---------')
        return (
            <div>
                {/* 直接從屬性取 */}
                <p>{this.props.name}</p>
                <p>{this.props.score}</p>
            </div>
        )
    }
}

export default class CommentList extends Component {
    constructor(props) {
        super(props)
        this.state = {
            commentList: []
        }
    }

    componentDidMount() {
        setInterval(() => {
            this.setState({
                commentList: [
                    {name: 'zhangsan', score: '99'},
                    {name: 'lisi', score: '100'}
                ]
            })
        }, 1000)
    }
    render() {
        return (
            <div>
                {/* 屬性展開 */}
                {this.state.commentList.map((item, index) => <Comment key={index} {...item}/>)}
            </div>
        )
    }
}

3. React.memo(v16.6.0 之後的版本, 函數式的組件也有了類似於React.PureComponent的函數渲染優化）

import React, { Component } from 'react'
const Comment = React.memo(function({name, score}){
    console.log('-----render!---------')
    return (
        <div>
            {/* 直接從屬性取 */}
            <p>{name}</p>
            <p>{score}</p>
        </div>
    )
})

export default class CommentList extends Component {
    constructor(props) {
        super(props)
        this.state = {
            commentList: []
        }
    }

    componentDidMount() {
        setInterval(() => {
            this.setState({
                commentList: [
                    {name: 'zhangsan', score: '99'},
                    {name: 'lisi', score: '100'}
                ]
            })
        }, 1000)
    }
    render() {
        return (
            <div>
                {/* 屬性展開 */}
                {this.state.commentList.map((item, index) => <Comment key={index} {...item}/>)}
            </div>
        )
    }
}