Virtualization in React Listview component

31 Oct 202423 minutes to read

UI virtualization loads only viewable list items in a view port which will increase ListView performance on loading large number of data.

Module injection

In order to use UI Virtualization, we need to inject its virtualization service in the App. This modules should be injected into the ListView using the Inject directive as like the below code snippet.

import { ListViewComponent, Inject, Virtualization } from '@syncfusion/ej2-react-lists';

....
....

      return (
          // specifies the tag to render the ListView component
          <ListViewComponent id='ui-list' dataSource={listData} enableVirtualization={true} >
              <Inject services={[Virtualization]} />
          </ListViewComponent>
      );

return (
// specifies the tag to render the ListView component
<ListViewComponent id='ui-list' dataSource={listData} enableVirtualization={true}>
              <Inject services={[Virtualization]}/>
          </ListViewComponent>);
export {};

Getting started

UI virtualization can be enabled in ListView by setting enableVirtualization property to true. It has two type of scroller

Window scroll - This scroller is used in ListView by default.

Container scroll - This will be used, if the height property of ListView was set.

index.jsx

import * as React from 'react';
import * as ReactDOM from "react-dom";
import { ListViewComponent, Inject, Virtualization } from '@syncfusion/ej2-react-lists';
function App() {
    // define the array of Json
    let listData;
    listData = [
        { text: "Nancy", id: "0" },
        { text: "Andrew", id: "1" },
        { text: "Janet", id: "2" },
        { text: "Margaret", id: "3" },
        { text: "Steven", id: "4" },
        { text: "Laura", id: "5" },
        { text: "Robert", id: "6" },
        { text: "Michael", id: "7" },
        { text: "Albert", id: "8" },
        { text: "Nolan", id: "9" }
    ];
    for (let i = 10; i <= 1010; i++) {
        let index = parseInt((Math.random() * 10).toString());
        listData.push({ text: listData[index].text, id: i.toString() });
    }
    return (
    // specifies the tag to render the ListView component
    <ListViewComponent id="ui-list" dataSource={listData} enableVirtualization={true}>
      <Inject services={[Virtualization]}/>
    </ListViewComponent>);
}
export default App;
ReactDOM.render(<App />, document.getElementById('element'));

index.tsx

import * as React from 'react';
import * as ReactDOM from "react-dom";
import { ListViewComponent, Inject, Virtualization } from '@syncfusion/ej2-react-lists';

function App() {
  // define the array of Json
  let listData: { [key: string]: string | object }[];
  listData = [
    { text: "Nancy", id: "0" },
    { text: "Andrew", id: "1" },
    { text: "Janet", id: "2" },
    { text: "Margaret", id: "3" },
    { text: "Steven", id: "4" },
    { text: "Laura", id: "5" },
    { text: "Robert", id: "6" },
    { text: "Michael", id: "7" },
    { text: "Albert", id: "8" },
    { text: "Nolan", id: "9" }
  ];
  for (let i: number = 10; i <= 1010; i++) {
    let index: number = parseInt((Math.random() * 10).toString());
    listData.push({ text: listData[index].text, id: i.toString() });
  }

  return (
    // specifies the tag to render the ListView component
    <ListViewComponent id="ui-list" dataSource={listData} enableVirtualization={true}>
      <Inject services={[Virtualization]} />
    </ListViewComponent>
  );
}
export default App;
ReactDOM.render(<App />, document.getElementById('element'));

We can use template property to customize list items in UI virtualization.

index.jsx

import * as React from 'react';
import * as ReactDOM from "react-dom";
import { ListViewComponent, Inject, Virtualization } from '@syncfusion/ej2-react-lists';
function App() {
    // define the array of Json
    let listData;
    listData = [
        { name: 'Nancy', icon: 'N', id: '0', },
        { name: 'Andrew', icon: 'A', id: '1' },
        { name: 'Janet', icon: 'J', id: '2' },
        { name: 'Margaret', imgUrl: 'https://ej2.syncfusion.com/react/demos/src/listview/images/margaret.png', id: '3' },
        { name: 'Steven', icon: 'S', id: '4' },
        { name: 'Laura', imgUrl: 'https://ej2.syncfusion.com/react/demos/src/listview/images/laura.png', id: '5' },
        { name: 'Robert', icon: 'R', id: '6' },
        { name: 'Michael', icon: 'M', id: '7' },
        { name: 'Albert', imgUrl: 'https://ej2.syncfusion.com/react/demos/src/listview/images/albert.png', id: '8' },
        { name: 'Nolan', icon: 'N', id: '9' }
    ];
    for (let i = 10; i <= 1010; i++) {
        let index = parseInt((Math.random() * 10).toString());
        listData.push({ name: listData[index].name, icon: listData[index].icon, imgUrl: listData[index].imgUrl, id: i.toString() });
    }
    function template(data) {
    return (
      <div className="e-list-wrapper e-list-avatar">
        <span className={`e-avatar e-avatar-small e-avatar-circle ${data.icon} ${data.imgUrl ? 'hideUI' : 'showUI'}`}>{data.icon}</span>
        <img className={`e-avatar e-avatar-circle ${data.imgUrl ? 'showUI' : 'hideUI'}`} src={data.imgUrl ? data.imgUrl : ' '} alt="" />
        <span className="e-list-content">{data.name}</span>
      </div>
    );
  } return (
    // specifies the tag to render the ListView component
    <ListViewComponent id='ui-list' dataSource={listData} enableVirtualization={true} template={template} cssClass='e-list-template' height={500} headerTitle="Contacts" showHeader={true}>
            <Inject services={[Virtualization]}/>
        </ListViewComponent>);
}
export default App;
ReactDOM.render(<App />, document.getElementById('element'));

index.tsx

import * as React from 'react';
import * as ReactDOM from "react-dom";
import { ListViewComponent, Inject, Virtualization } from '@syncfusion/ej2-react-lists';

function App() {
    // define the array of Json
    let listData: { [key: string]: string | object }[];
    listData = [
        { name: 'Nancy', icon: 'N', id: '0', },
        { name: 'Andrew', icon: 'A', id: '1' },
        { name: 'Janet', icon: 'J', id: '2' },
        { name: 'Margaret', imgUrl: 'https://ej2.syncfusion.com/react/demos/src/listview/images/margaret.png', id: '3' },
        { name: 'Steven', icon: 'S', id: '4' },
        { name: 'Laura', imgUrl: 'https://ej2.syncfusion.com/react/demos/src/listview/images/laura.png', id: '5' },
        { name: 'Robert', icon: 'R', id: '6' },
        { name: 'Michael', icon: 'M', id: '7' },
        { name: 'Albert', imgUrl: 'https://ej2.syncfusion.com/react/demos/src/listview/images/albert.png', id: '8' },
        { name: 'Nolan', icon: 'N', id: '9' }
    ];
    for (let i: number = 10; i <= 1010; i++) {
        let index: number = parseInt((Math.random() * 10).toString());
        listData.push({ name: listData[index].name, icon: listData[index].icon, imgUrl: listData[index].imgUrl, id: i.toString() });
    }
       // Set customized list template
    function template(data: any) {
        return (
            <div className="e-list-wrapper e-list-avatar">
                <span className={`e-avatar e-avatar-circle ${data.icon} ${data.imgUrl ? 'hideUI' : 'showUI'}`}>{data.icon}</span>
                <img className={`e-avatar e-avatar-circle ${data.imgUrl ? 'showUI' : 'hideUI'}`} src={data.imgUrl ? data.imgUrl : ' '} />
                <span className="e-list-content">{data.name}</span>
            </div>
        );
    }
    return (
        // specifies the tag to render the ListView component
        <ListViewComponent id='ui-list' dataSource={listData} enableVirtualization={true} template={template} height={500} cssClass='e-list-template' headerTitle="Contacts" showHeader={true}>
            <Inject services={[Virtualization]} />
        </ListViewComponent>
    );
}
export default App;
ReactDOM.render(<App />, document.getElementById('element'));

index.css

#ui-list.e-listview {
        margin: auto;
        max-width: 325px;
        line-height: initial;
        border: 1px solid lightgray;
    }

    /* ListView header alignment */

    #ui-list.e-listview .e-list-header {
        height: 50px
    }

    #ui-list.e-listview .e-list-header .e-text {
        line-height: 18px
    }

    /* ListView template customization */

    #ui-list.e-listview .showUI {
        display: flex;
        align-items: center;
        justify-content: center;
        border-radius: 50%;
    }
    #ui-list.e-listview .hideUI {
        display: none;
    }

    #ui-list.e-listview .e-list-item {
        padding: 3px 0;
    }

    #ui-list.e-listview .R {
        background: lightgrey;
    }

    #ui-list.e-listview .M {
        background: pink;
    }

    #ui-list.e-listview .A {
        background: lightgreen;
    }

    #ui-list.e-listview .S {
        background: lightskyblue;
    }

    #ui-list.e-listview .J {
        background: orange;
    }

    #ui-list.e-listview .N {
        background: lightblue;
    }

Conditional rendering

We have also provided following conditional rendering support for template and groupTemplate.

Name	Syntax
conditional class	<div class="${ $id % 2 === 0 ? 'even-list' : 'odd-list'}"></div>
conditional attribute	<div id="${ $id % 2 === 0 ? 'even-list' : 'odd-list'}"></div>
conditional text content	<div>${ $id % 2 === 0 ? 'even-list' : 'odd-list'}</div>

In the below sample, we have applied light blue for even list and light coral for odd list based on the conditional class.

index.jsx

import * as React from 'react';
import * as ReactDOM from "react-dom";
import { ListViewComponent, Inject, Virtualization } from '@syncfusion/ej2-react-lists';
function App() {
    // define the array of Json
    let listData;
    listData = [
        { text: "Nancy", id: "0" },
        { text: "Andrew", id: "1" },
        { text: "Janet", id: "2" },
        { text: "Margaret", id: "3" },
        { text: "Steven", id: "4" },
        { text: "Laura", id: "5" },
        { text: "Robert", id: "6" },
        { text: "Michael", id: "7" },
        { text: "Albert", id: "8" },
        { text: "Nolan", id: "9" }
    ];
    for (let i = 10; i <= 1010; i++) {
        let index = parseInt((Math.random() * 10).toString());
        listData.push({ text: listData[index].text, id: i.toString() });
    }
    let template = "<div id=\"list-container\" class=\"${ $id % 2 === 0 ? 'even-list' : 'odd-list' }\" > ${text} </div>";
    return (
    // specifies the tag to render the ListView component
    <ListViewComponent id="ui-list" dataSource={listData} enableVirtualization={true} template={template} height={500}>
      <Inject services={[Virtualization]}/>
    </ListViewComponent>);
}
export default App;
ReactDOM.render(<App />, document.getElementById('element'));

index.tsx

import * as React from 'react';
import * as ReactDOM from "react-dom";
import { ListViewComponent, Inject, Virtualization } from '@syncfusion/ej2-react-lists';

function App() {  
  // define the array of Json
  let listData: { [key: string]: string | object }[];
  listData = [
    { text: "Nancy", id: "0" },
    { text: "Andrew", id: "1" },
    { text: "Janet", id: "2" },
    { text: "Margaret", id: "3" },
    { text: "Steven", id: "4" },
    { text: "Laura", id: "5" },
    { text: "Robert", id: "6" },
    { text: "Michael", id: "7" },
    { text: "Albert", id: "8" },
    { text: "Nolan", id: "9" }
  ];
  for (let i: number = 10; i <= 1010; i++) {
    let index: number = parseInt((Math.random() * 10).toString());
    listData.push({ text: listData[index].text, id: i.toString() });
  }

  let template: string =
    "<div id=\"list-container\" class=\"${ $id % 2 === 0 ? 'even-list' : 'odd-list' }\" > ${text} </div>";

  return (
    // specifies the tag to render the ListView component
    <ListViewComponent
      id="ui-list"
      dataSource={listData}
      enableVirtualization={true}
      template={template}
      height={500}
    >
      <Inject services={[Virtualization]} />
    </ListViewComponent>
  );
}
export default App;
ReactDOM.render(<App />, document.getElementById('element'));