Implement Efficient Virtual Scrolling with Vue.js

Introduction

In this project, you will learn how to implement a virtual scrolling list using Vue.js. Virtual scrolling is a technique that only renders the visible area of a large dataset, rather than rendering or partially rendering the data in the non-visible area. This achieves extremely high rendering performance and is suitable for rendering a large number of data with a small volume.

👀 Preview

🎯 Tasks

In this project, you will learn:

• How to load and render data asynchronously using the axios library
• How to implement virtual scrolling functionality to only render the visible list items
• How to calculate the start and end indices of the visible list items based on the current scroll position
• How to optimize the rendering performance by using a buffer to render additional list items outside the visible area

🏆 Achievements

After completing this project, you will be able to:

• Implement virtual scrolling functionality to improve rendering performance
• Load and render data asynchronously in a Vue.js component
• Calculate the visible list items based on the current scroll position
• Use a buffer to prevent a white screen during scrolling

Skills Graph

Set Up the Project Structure

In this step, you will learn about the project structure and the files involved in the login functionality.

The project directory structure is as follows:

The initial code for this question has already been provided. Open the coding environment, and the directory structure is as follows:

├── js
│   ├── axios.min.js
│   ├── http-vue-loader.js
│   └── vue.min.js
├── data.json
├── index.html
└── virtual-scroll-list.vue

Where:

• js/axios.min.js is the axios request library file.
• js/vue.min.js and js/http-vue-loader.js are Vue.js library related files.
• data.json is the data file to be requested.
• index.html is the main page.
• virtual-scroll-list.vue is the component file that needs to be completed.

Click on Go Live button in the bottom right corner of WebIDE, to run the project.

Next, open "Web 8080" on the top of the VM and refresh it manually and you will see the page. The initial effect is an empty list box.

Asynchronous Data Loading and Rendering

In this step, you will learn how to load and render data asynchronously using the axios library.

1. Open the virtual-scroll-list.vue file.
2. In the mounted() lifecycle hook, use axios to make a request to the data.json file and populate the list data:

mounted() {
  // TODO: Completion of data requests
  axios("./data.json").then((res) => {
    this.list = res.data;
    this.totalHeight = this.list.length * this.itemHeight; // calculate the total height
  });
}

This will fetch the data from the data.json file and store it in the list data property. The totalHeight property is also calculated based on the length of the list and the itemHeight.

After completing this step, the initial list should be rendered with the data loaded from the data.json file.

Implementing Virtual Scrolling

In this step, you will learn how to implement the virtual scrolling functionality.

1. Open the virtual-scroll-list.vue file.
2. Implement the scroll event handler:

methods: {
  scroll(e) {
    this.start = Math.floor(e.currentTarget.scrollTop / this.itemHeight);
  },
}

The scroll event handler calculates the start index of the visible list items based on the current scroll position.

After completing this step, the virtual scrolling functionality should be implemented, and the list items should only be rendered when they are visible in the viewport. The final effect is shown in the following figure.

Summary

Congratulations! You have completed this project. You can practice more labs in LabEx to improve your skills.