Add a stylesheet

Cascading stylesheets represent one of the most common ways to customize the user experience for an application. This tutorial illustrates how to add a stylesheet when you use React to create a new front-end for your project. If you already know how to add cascading stylesheets (CSS) to a React-based project, you can skip this tutorial.

This tutorial illustrates using the React framework to manage the Document Object Model (DOM) for your canister. Because React has its own custom DOM syntax, you need to modify the webpack configuration to compile the front-end code, which is written in JSX. For more information about learning to use React and JSX, see Getting started on the React website.

Before you begin

Before starting the tutorial, verify the following:

  • You have node.js installed for front-end development and can install packages using npm install in your project. For information about installing node for your local operating system and package manager, see the Node website.

  • You have downloaded and installed the DFINITY Canister SDK package as described in Download and install.

  • You have installed the Visual Studio Code plugin for Motoko as described in Install the language editor plug-in if you are using Visual Studio Code as your IDE.

  • You have stopped any Internet Computer network processes running on the local computer.

Because of significant changes to the handling of HTTP requests and front-end assets, this tutorial requires you to use the DFINITY Canister SDK version 0.7.0 or later. For an overview of what’s changed, see this article.

Create a new project

To create a new project directory for your custom front-end application:

  1. Open a terminal shell on your local computer, if you don’t already have one open.

  2. Change to the folder you are using for your Internet Computer projects, if you are using one.

  3. Verify that you have node.js installed locally, if necessary.

  4. Create a new project by running the following command:

    dfx new contacts
  5. Change to your project directory by running the following command:

    cd contacts

Install the React framework

if you’ve never used React before, you might want to explore the Intro to React tutorial or the React website before editing the front-end code.

To install required framework modules:

  1. Install the React module by running the following command:

    npm install --save react react-dom
  2. Install the required TypeScript language compiler loader by running the following command:

    npm install --save-dev typescript ts-loader
  3. Install the required style loaders by running the following command:

    npm install --save-dev style-loader css-loader

    If the npm install command reports a vulnerability, you might also want to run the npm audit fix command to attempt to fix the vulnerability reported before continuing.

    As an alternative to installing these modules, you can edit the default package.json file to add dependencies for your project.
      "name": "contacts_assets",
      "version": "0.1.0",
      "description": "",
      "keywords": [],
      "scripts": {
        "build": "webpack"
      "devDependencies": {
        "assert": "2.0.0",
        "buffer": "6.0.3",
        "css-loader": "^5.2.1",
        "events": "3.3.0",
        "html-webpack-plugin": "5.3.1",
        "process": "0.11.10",
        "stream-browserify": "3.0.0",
        "style-loader": "^2.0.0",
        "terser-webpack-plugin": "5.1.1",
        "ts-loader": "^8.1.0",
        "typescript": "^4.2.4",
        "util": "0.12.3",
        "webpack-cli": "4.5.0",
        "webpack": "5.24.4"
      "dependencies": {
        "@dfinity/agent": "0.9.2",
        "@dfinity/candid": "0.9.2",
        "@dfinity/principal": "0.9.2",
        "react-dom": "^17.0.2",
        "react": "^17.0.2"

    The version of the JavaScript agent in this example package.json file is 0.9.2. In most cases, however, you would want to use the latest version of the agent available. When you create a new project, the dfx new command automatically retrieves the latest version of the JavaScript agent for you. You can also manually retrieve the latest version after creating a project by running the npm install --save @dfinity/agent command.

Modify the default program

For this tutorial, you are going to modify the main program to with code that allows you to store and look up contact information.

To modify the default program:

  1. Open the src/contacts/ file in a text editor and delete the existing content.

  2. Copy and paste the following sample code into the file:

    import List "mo:base/List";
    import AssocList "mo:base/AssocList";
    actor Contact {
      var contacts : ContactsMap = List.nil();
      type Name = Text;
      type Phone = Nat;
      type Entry = {
        name : Name;
        address1 : Text;
        address2 : Text;
        email : Text;
        phone : Phone;
      type ContactsMap = AssocList.AssocList<Name, Entry>;
      func nameEq(lhs : Name, rhs : Name) : Bool {
        return lhs == rhs;
      public func insert(name : Name, address1 : Text, address2 : Text, email : Text, phone : Phone) : async () {
         let newEntry : Entry = {
         let (newContacts, _) = AssocList.replace(
           func(n: Name, m: Name) : Bool { n == m },
         contacts := newContacts;
      public query func lookup(name : Name) : async ?Entry {
        return AssocList.find(contacts, name, nameEq);
  3. Save your changes and close the file to continue.

Modify the front-end files

You are now ready to create a new front-end for your program.

  1. Open the webpack configuration file (webpack.config.js) in a text editor.

  2. Modify the front-end entry to replace the default index.html with index.jsx.

    entry: {
      // The frontend.entrypoint points to the HTML file for this build, so we need
      // to replace the extension to `.js`.
      index: path.join(__dirname, asset_entry).replace(/\.html$/, ".jsx"),
  3. Locate the commented example for the module key above the plugins section, then uncomment the following lines:

    module: {
      rules: [
        { test: /\.(js|ts)x?$/, loader: "ts-loader" },
        { test: /\.css$/, use: ['style-loader','css-loader'] }

    These settings enable your program to use the ts-loader compiler and to import CSS files.

  4. Save your changes and close the webpack.config.js file to continue.

  5. Create a new file named tsconfig.json in the root directory for your project.

  6. Open the tsconfig.json file in a text editor, then copy and paste the following into the file:

        "compilerOptions": {
          "target": "es2018",        /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019' or 'ESNEXT'. */
          "lib": ["ES2018", "DOM"],  /* Specify library files to be included in the compilation. */
          "allowJs": true,           /* Allow javascript files to be compiled. */
          "jsx": "react",            /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
        "include": ["src/**/*"],
  7. Save your changes and close the tsconfig.json file to continue.

Add a stylesheet to your project

You are now ready to create a new cascading stylesheet and add it to your project.

To add a stylesheet:

  1. Change to the src/contacts_assets/assets directory.

    cd src/contacts_assets/assets/
  2. Open the main.css file in a text editor and delete the existing content.

  3. Define some style properties for the front-end.

    For example, copy and paste the following sample styles into the file:

    html {
        background-color: bisque;
    body {
        font-family: Arial, Helvetica, sans-serif;
        display: block;
        margin: 10px;
    h1 {
        color: darkblue;
        font-size: 32px;
    } {
        margin: 30px 20px 30px 20px;
    .new-entry > div {
        margin-bottom: 15px;
    table {
        margin-top: 12px;
        border-top: 1px solid darkblue;
        border-bottom: 1px solid darkblue;
    #form {
        margin: 30px 0 30px 20px;
    button {
        line-height: 20px;
    #lookupName {
        margin-right: 12px;
  4. Save your changes and close the main.css file to continue.

  5. Change to the src/contacts_assets/src directory.

    cd ../src
  6. Open the default index.js file in a text editor and delete the existing content.

  7. Copy and paste the following sample code into the index.js file:

    import * as React from "react";
    import { render } from "react-dom";
    import { contacts } from "../../declarations/contacts";
    const Contact = () => {
      async function doInsert() {
        let name = document.getElementById("newEntryName").value;
        let add1 = document.getElementById("newEntryAddress1").value;
        let add2 = document.getElementById("newEntryAddress2").value;
        let email = document.getElementById("newEntryEmail").value;
        let phone = document.getElementById("newEntryPhone").value;
        contacts.insert(name, add1, add2, email, parseInt(phone, 10));
      async function lookup() {
        let name = document.getElementById("lookupName").value;
        contacts.lookup(name).then((opt_entry) => {
          let entry;
          if (opt_entry.length == 0) {
            entry = { name: "", description: "", phone: "" };
          } else {
            entry = opt_entry[0];
          document.getElementById("newEntryName").value =;
          document.getElementById("newEntryAddress1").value = entry.address1;
          document.getElementById("newEntryAddress2").value = entry.address2;
          document.getElementById("newEntryEmail").value =;
          document.getElementById("newEntryPhone").value =;
      return (
        <div className="new-entry">
          <h1>My Contacts</h1>
            Add or update contact information:
            <form id="contact">
                      <input id="newEntryName"></input>
                    <td>Address 1 (street):</td>
                      <input id="newEntryAddress1"></input>
                    <td>Address 2 (city and state):</td>
                      <input id="newEntryAddress2"></input>
                      <input id="newEntryEmail"></input>
                      <input id="newEntryPhone" type="number"></input>
            <button onClick={() => doInsert()}>Add Contact</button>
            Lookup name:{" "}
            <input id="lookupName" style={{ lineHeight: "20px" }}></input>
            <button onClick={() => lookup()}>Lookup</button>
    document.title = "DFINITY CONTACT EXAMPLE";
    render(<Contact />, document.getElementById("contacts"));
  8. Rename the modified index.js file as index.jsx by running the following command:

    mv index.js index.jsx
  9. Open the default src/contacts_assets/src/index.html file in a text editor, then replace main.css as the stylesheet file name with mycontacts.css and update the body contents with <div id="contacts"></div>.

    For example:

    <!DOCTYPE html>
    <html lang="en">
        <meta charset="UTF-8" />
        <meta name="viewport" content="width=device-width" />
        <base href="/" />
        <link type="text/css" rel="stylesheet" href="main.css" />
          <div id="contacts"></div>
  10. Navigate back to the root of your project directory.

    For example:

    cd ../../..

Start the local network

Before you can build the contacts project, you need to connect to the Internet Computer network either running locally in your development environment or running remotely on a subnet that you can access.

To start the network locally:

  1. Open a new terminal window or tab on your local computer.

  2. Start the Internet Computer network on your local computer by running the following command:

    dfx start --background

    After the local Internet Computer network completes its startup operations, you can continue to the next step.

Register, build, and deploy the application

After you connect to the Internet Computer network running locally in your development environment, you can register, build, and deploy your application locally.

To deploy the application:

  1. Check that you are still in the root directory for your project, if needed.

  2. Register, build, and deploy your application by running the following command:

    dfx deploy

    The dfx deploy command output displays information about the operations it performs.

    Keep in mind that because you are running the Internet Computer locally, the identifiers displayed when you run the dfx deploy command are only valid on the local network.

    To deploy canisters on an external Internet Computer network, you must connect to that network using the --network command-line option and a specific network name or address to register identifiers on that network. For example, to deploy on the Internet Computer using the reserve network alias ic, you would run a command similar the following:

    dfx deploy --network=ic
  3. Start the Webpack development server:

    npm start

View the front-end

You can now access the front-end for the contacts program by entering the canister identifier for the assets canister in a browser.

To view the front-end:

  1. Open a browser and navigate to the http://localhost:8080.

  2. Verify that you are prompted with a My Contacts form.

    For example:

    Sample front-end

  3. Create one or more test records by entering text in the Name, Address, and Email input fields and a number in the Phone input field, then clicking Add Contact.

  4. Clear the form fields and type a contact name in the Lookup name field, then click Lookup to see the stored contact information.

    Keep in mind that the Lookup name you type must be an exact match for the name of a contact you added.

Modify the stylesheet and test your changes

After viewing the Contacts application, you might want to make some changes.

To change stylesheet properties:

  1. Open the src/contacts_assets/public/mycontacts.css file in a text editor and modify its style settings.

    For example, you might want to change the background color or style the input form.

    You should see the changes update immediately in your open browser window.

Modify the front-end or back-end code

If you want to explore further, you might want to experiment with modifying the front-end or back-end code for this tutorial. For example, you might want try modifying the tutorial to do the following:

  • Change the front-end code to clear the input fields after adding a new contact, for example, as part of an onClick event.

  • Change the Motoko program functions to do partial instead of exact string matching on the Name field. (You will need to run dfx deploy to test your changes on the local replica)

  • Change the Motoko program to allow lookups based on a different field.

Stop the local network

After you finish experimenting with your program, you can stop the local Internet Computer network so that it doesn’t continue running in the background.

To stop the local network:

  1. In the terminal that displays your webpack dev server, press Control-C to interrupt the development server.

  2. Stop the Internet Computer network by running the following command:

    dfx stop