Tutorial: Handle authentication flows in a Vanilla JavaScript SPA

Article
09/24/2024

This tutorial is part 3 of a series that demonstrates building a Vanilla JavaScript (JS) single-page application (SPA) and preparing it for authentication. In part 2 of this series, you created a Vanilla JS SPA and prepared it for authentication with your external tenant. In this tutorial, you learn how to handle authentication flows in your app by adding Microsoft Authentication Library (MSAL) components.

In this tutorial;

Configure the settings for the application
Add code to authRedirect.js to handle the authentication flow
Add code to authPopup.js to handle the authentication flow

Prerequisites

Tutorial: Prepare your external tenant to authenticate users in a Vanilla JavaScript SPA.

Edit the authentication configuration file

Open public/authConfig.js and add the following code snippet:

import { LogLevel } from '@azure/msal-browser';

/**
* Configuration object to be passed to MSAL instance on creation. 
* For a full list of MSAL.js configuration parameters, visit:
* https://github.com/AzureAD/microsoft-authentication-library-for-js/blob/dev/lib/msal-browser/docs/configuration.md 
*/

export const msalConfig = {
    auth: {
        clientId: 'Enter_the_Application_Id_Here', // This is the ONLY mandatory field that you need to supply.
        authority: 'https://Enter_the_Tenant_Subdomain_Here.ciamlogin.com/', // Replace the placeholder with your tenant subdomain 
        redirectUri: '/', // Points to window.location.origin. You must register this URI on Azure Portal/App Registration.
        postLogoutRedirectUri: '/', // Indicates the page to navigate after logout.
        navigateToLoginRequestUrl: false, // If "true", will navigate back to the original request location before processing the auth code response.
    },
    cache: {
        cacheLocation: 'sessionStorage', // Configures cache location. "sessionStorage" is more secure, but "localStorage" gives you SSO between tabs.
        storeAuthStateInCookie: false, // Set this to "true" if you are having issues on IE11 or Edge
    },
    system: {
        loggerOptions: {
            loggerCallback: (level, message, containsPii) => {
                if (containsPii) {
                    return;
                }
                switch (level) {
                    case LogLevel.Error:
                        console.error(message);
                        return;
                    case LogLevel.Info:
                        console.info(message);
                        return;
                    case LogLevel.Verbose:
                        console.debug(message);
                        return;
                    case LogLevel.Warning:
                        console.warn(message);
                        return;
                    default:
                        return;
                }
            },
        },
    },
};

/**
* Scopes you add here will be prompted for user consent during sign-in.
* By default, MSAL.js will add OIDC scopes (openid, profile, email) to any login request.
* For more information about OIDC scopes, visit: 
* https://docs.microsoft.com/en-us/azure/active-directory/develop/v2-permissions-and-consent#openid-connect-scopes
*/
export const loginRequest = {
    scopes: [],
};

Replace the following values with the values from the Azure portal:
- Find the Enter_the_Application_Id_Here value and replace it with the Application ID (clientId) of the app you registered in the Microsoft Entra admin center.
  - In Authority, find Enter_the_Tenant_Subdomain_Here and replace it with the subdomain of your tenant. For example, if your tenant primary domain is contoso.onmicrosoft.com, use contoso. If you don't have your tenant name, learn how to read your tenant details.
Save the file.

Use custom URL domain (Optional)

Use a custom domain to fully brand the authentication URL. From a user perspective, users remain on your domain during the authentication process, rather than being redirected to ciamlogin.com domain name.

Use the following steps to use a custom domain:

Use the steps in Enable custom URL domains for apps in external tenants to enable custom URL domain for your external tenant.
In your authConfig.js file, locate then auth object, then:
1. Update the value of the authority property to https://Enter_the_Custom_Domain_Here/Enter_the_Tenant_ID_Here. Replace Enter_the_Custom_Domain_Here with your custom URL domain and Enter_the_Tenant_ID_Here with your tenant ID. If you don't have your tenant ID, learn how to read your tenant details.
2. Add knownAuthorities property with a value [Enter_the_Custom_Domain_Here].

After you make the changes to your authConfig.js file, if your custom URL domain is login.contoso.com, and your tenant ID is aaaabbbb-0000-cccc-1111-dddd2222eeee, then your file should look similar to the following snippet:

//...
const msalConfig = {
    auth: {
        authority: process.env.AUTHORITY || 'https://login.contoso.com/aaaabbbb-0000-cccc-1111-dddd2222eeee', 
        knownAuthorities: ["login.contoso.com"],
        //Other properties
    },
    //...
};

Adding code to the redirection file

A redirection file is required to handle the response from the sign-in page. It's used to extract the access token from the URL fragment and use it to call the protected API. It's also used to handle errors that occur during the authentication process.

Open public/authRedirect.js and add the following code snippet:

// Create the main myMSALObj instance
// configuration parameters are located at authConfig.js
const myMSALObj = new msal.PublicClientApplication(msalConfig);

let username = "";

/**
* A promise handler needs to be registered for handling the
* response returned from redirect flow. For more information, visit:
* https://github.com/AzureAD/microsoft-authentication-library-for-js/blob/dev/lib/msal-browser/docs/initialization.md#redirect-apis
*/
myMSALObj.handleRedirectPromise()
    .then(handleResponse)
    .catch((error) => {
        console.error(error);
    });

function selectAccount() {

    /**
    * See here for more info on account retrieval: 
    * https://github.com/AzureAD/microsoft-authentication-library-for-js/blob/dev/lib/msal-common/docs/Accounts.md
    */

    const currentAccounts = myMSALObj.getAllAccounts();

    if (!currentAccounts) {
        return;
    } else if (currentAccounts.length > 1) {
        // Add your account choosing logic here
        console.warn("Multiple accounts detected.");
    } else if (currentAccounts.length === 1) {
        username = currentAccounts[0].username
        welcomeUser(currentAccounts[0].username);
        updateTable(currentAccounts[0]);
    }
}

function handleResponse(response) {

    /**
    * To see the full list of response object properties, visit:
    * https://github.com/AzureAD/microsoft-authentication-library-for-js/blob/dev/lib/msal-browser/docs/request-response-object.md#response
    */

    if (response !== null) {
        username = response.account.username
        welcomeUser(username);
        updateTable(response.account);
    } else {
        selectAccount();

    }
}

function signIn() {

    /**
    * You can pass a custom request object below. This will override the initial configuration. For more information, visit:
    * https://github.com/AzureAD/microsoft-authentication-library-for-js/blob/dev/lib/msal-browser/docs/request-response-object.md#request
    */

    myMSALObj.loginRedirect(loginRequest);
}

function signOut() {

    /**
    * You can pass a custom request object below. This will override the initial configuration. For more information, visit:
    * https://github.com/AzureAD/microsoft-authentication-library-for-js/blob/dev/lib/msal-browser/docs/request-response-object.md#request
    */

    // Choose which account to logout from by passing a username.
    const logoutRequest = {
        account: myMSALObj.getAccountByUsername(username),
        postLogoutRedirectUri: '/signout', // remove this line if you would like navigate to index page after logout.

    };

    myMSALObj.logoutRedirect(logoutRequest);
}

Save the file.

Adding code to the authPopup.js file

The application uses authPopup.js to handle the authentication flow when the user signs in using the pop-up window. The pop-up window is used when the user is already signed in and the application needs to get an access token for a different resource.

Open public/authPopup.js and add the following code snippet:

// Create the main myMSALObj instance
// configuration parameters are located at authConfig.js
const myMSALObj = new msal.PublicClientApplication(msalConfig);

let username = "";

function selectAccount () {

    /**
     * See here for more info on account retrieval: 
     * https://github.com/AzureAD/microsoft-authentication-library-for-js/blob/dev/lib/msal-common/docs/Accounts.md
     */

    const currentAccounts = myMSALObj.getAllAccounts();

    if (!currentAccounts  || currentAccounts.length < 1) {
        return;
    } else if (currentAccounts.length > 1) {
        // Add your account choosing logic here
        console.warn("Multiple accounts detected.");
    } else if (currentAccounts.length === 1) {
        username = currentAccounts[0].username
        welcomeUser(currentAccounts[0].username);
        updateTable(currentAccounts[0]);
    }
}

function handleResponse(response) {

    /**
     * To see the full list of response object properties, visit:
     * https://github.com/AzureAD/microsoft-authentication-library-for-js/blob/dev/lib/msal-browser/docs/request-response-object.md#response
     */

    if (response !== null) {
        username = response.account.username
        welcomeUser(username);
        updateTable(response.account);
    } else {
        selectAccount();
    }
}

function signIn() {

    /**
     * You can pass a custom request object below. This will override the initial configuration. For more information, visit:
     * https://github.com/AzureAD/microsoft-authentication-library-for-js/blob/dev/lib/msal-browser/docs/request-response-object.md#request
     */

    myMSALObj.loginPopup(loginRequest)
        .then(handleResponse)
        .catch(error => {
            console.error(error);
        });
}

function signOut() {

    /**
     * You can pass a custom request object below. This will override the initial configuration. For more information, visit:
     * https://github.com/AzureAD/microsoft-authentication-library-for-js/blob/dev/lib/msal-browser/docs/request-response-object.md#request
     */

    // Choose which account to logout from by passing a username.
    const logoutRequest = {
        account: myMSALObj.getAccountByUsername(username),
        mainWindowRedirectUri: '/signout'
    };

    myMSALObj.logoutPopup(logoutRequest);
}

selectAccount();

Save the file.

Next step

Part 4: Sign in and sign out of the Vanilla JS SPA

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