joppot

コピペで絶対動く。説明を妥協しない

プログラミング

Lazy load image with react-lazyload

投稿日:2018年12月3日 更新日:


Abstract

Hello everyoen it’s me candle. This time let’s make a delayed loading of images with react-lazyload. The problem of SPA is the delay at the time of initial loading. Among them, we feel that the site with many images is even late. Let’s try it.

Condition

Nothing

Prepare

If you have already developing react project, use it.
But you don’t have yet or try to test. Generate it with this command.

create-react-app imageloader-sample
cd imageloader-sample

We will prepare images for samples with Faker.js, so install it.

yarn add faker

Ready to develop.

Make a sample code

Open the src/App.js and edit like this.

import React, { Component } from 'react'
import Faker from 'faker'

class App extends Component {
  constructor(props) {
    super(props)
    this.state = {
      users: [],
    }
  }
  componentWillMount() {
    for (let i = 0; i < 30; i++) {
      const user = {
        name: Faker.internet.userName(),
        email: Faker.internet.email(),
        avatar: Faker.internet.avatar(),
      }
      this.setState(prevState => ({
        users: [...prevState.users, user],
      }))
    }
  }

  renderUsers(user) {
    return (
      <div style={{ border: 'solid 1px #eee' }}>
        <img src={user.avatar} alt={user.name} width="50" height="50" />
        <h4>Name: {user.name}</h4>
        <h4>Email: {user.email}</h4>
      </div>
    )
  }

  render() {
    return <div>{this.state.users.map(user => this.renderUsers(user))}</div>
  }
}

export default App

Execute this code and you can see this screen.

It displays the thirty images on the screen.

Use React-lazyload

First we will install react-lazyload.

yarn add react-lazyload

Open the src/App.js and edit.

import React, { Component } from 'react'
import Faker from 'faker'

import LazyLoad from 'react-lazyload'

class App extends Component {
  constructor(props) {
    super(props)
    this.state = {
      users: [],
    }
  }
  componentWillMount() {
    for (let i = 0; i < 30; i++) {
      const user = {
        name: Faker.internet.userName(),
        email: Faker.internet.email(),
        avatar: Faker.internet.avatar(),
      }
      this.setState(prevState => ({
        users: [...prevState.users, user],
      }))
    }
  }

  renderUsers(user) {
    return (
      <div style={{ border: 'solid 1px #eee' }}>
        <LazyLoad width="50" height="50" once>
          <img src={user.avatar} alt={user.name} width="50" height="50" />
        </LazyLoad>
        <h4>Name: {user.name}</h4>
        <h4>Email: {user.email}</h4>
      </div>
    )
  }

  render() {
    return <div>{this.state.users.map(user => this.renderUsers(user))}</div>
  }
}

export default App

In this way, only the minimum required image is loaded, and the rest are loaded lazily.

It went good.

Conclusion

It is better to do lazy loading of images absolutely so let’s try it out.

スポンサードリンク

If you think this article is good, share it please

-プログラミング
-,

執筆者:


comment

Your email address will not be published. Required fields are marked *

関連記事

Create the simplest drop down menu in React

Abstract Hello everyone it’s me candle. In this time we will make a most simple drop down menu. Condition Knowledge of react Preparation We create a react project with the below command. create-react-app hello-menu Open src/App.js and write this. import React, { Component } from 'react' class App extends Component { render() { return ( <div> <p>hello menu</p> </div> ) } } export default App Create a components directory in the src directory. mkdir src/components Create a DropDownMenu.js file in the src/components directory. touch src/components/DropDownMenu.js Now on ready. Create a Drop down menu Open the src/components/DropDownMenu.js and write these. import …

Remove or allow the html tag with javascript + React and take measures against XSS

Abstract Hello everyone it’s me candle. In this time, we will write a program which displays only the permitted html tags by React and delete other tags. Notice, displaying originally html contents, it may has a security risk such as XSS. First of all, I am not a security expert, so there is a possibility of a bug in the code. Of course, I check it and test it as long as I do. If you find any vulnerabilities in the code, it would be helpful if you point out it in the post comment form. Condition Nothing Preparation of …

React Native slows down when debugging on Google Chrome

English 日本語 Abstract Hello everybody, It’s candle. This time, we will solve the problem that using simulator is going to slow down when debugging on the Google Chrome Anyway, It is solved in a simple way. we use Chromium instead of Google Chrome. Premise React development environment has been established

Customize wordpress bogo plugin’s short code

English 日本語 Abstract Hello everyone, It’s me candle. In this time, I will show you how to customize wordpress bogo short code. The items to introduce are these. The flag display or hide Change the text Related article How to change the language form “en-US” to “en” by wordpres bogo Precondition WordPress bogo has been installed You can edit the theme of wordpress

Use react-simple-format in React web

Abstract Hello everyone it’s me candle. In this article we will use simple-format in react. Simple format is famous for Ruby on Rails and is commonly used. React has a legacy react-simple-format and 16g’s made. The legacy lib is not useful, so I choose 16g’s made. https://github.com/16g/react-simple-format Condition Nothing Create project If you already have a React project please use it. If not, use the following command to create it. create-react-app simple_format_sample cd simple_format_sample How to use react-simple-format First install it. yarn add @16g/react-simple-format Open a appropriate component file. I write it in src/App.js. import React, { Component } from …


I work in the venture company as a CTO. I start to write program in University, first I learned java, C++ and PHP. In the company, I'm developing web services by Rails. I do like to automation.