Walkthrough: Integrate Square Payments In a Website

This topic provides a walkthrough with step-by-step instructions to set up a simple website integrated with Square for payments. We’ll keep the exercise simple and build a basic form that just takes a credit card on a web page as shown:

At the end of the exercise, we provide links to topics that explain how you can add other payment sources, such as digital wallets, to your website. The SqPaymentForm technical reference is available when you need more information about one of the payment form library types or functions.

Processing payments in a website using Square is a 2-step process:

You follow this process to set up a website. You then test the setup by taking a payment. We also show you how to review the payment in the Seller dashboard. At the end, we explain a variation of the payment form called single-element payment form.

Before you begin, note the following:

• The walkthrough uses a Node.js web server project template that we provide. We chose Node.js because it is easy to set up and test. After finishing this walkthrough, you can explore similar examples in other languages we provide on GitHub. For more information, see connect-api-examples.

• We use the v2 Sandbox environment for testing. In the sandbox, you don’t charge your real credit card, instead use a fake card Square provides for Sandbox testing. After taking a payment, we show you how the payment appears in the Sandbox Seller Dashboard.

• If you are new to Square payment forms, you should follow the step-by-step instructions. A complete sample is available on GitHub for download if you want to check the code in your project at the end of this walkthrough.

Get ready

To prepare for this walkthrough, you do 3 things:

• Install Node.js and npm (a Node.js package manager).

• Get your application credentials from Square’s Developer Dashboard.

• Download the project template created for this exercise

Install Node.js and npm

When you install Node.js, you also get npm. For instructions, see Node.js.

Get sandbox application credentials

We use the v2 Sandbox environment for testing. Therefore, you use your sandbox credentials.

Developer Dashboard in Sandbox Settings mode

You use application ID to obtain a nonce in step 1, and the personal access token to take a payment using the Payments API in step 2.

Download project template

For this exercise, you start with a predefined project template to set up your initial web server. Do the following:

Now you are ready to build a web page that embeds the SqPaymentForm.

Step 1: Generate a secure single use token (nonce)

In this step, you will do the following:

• Build a web page with SqPaymentForm embedded in it.

• Test the page by submitting card information and verifying that you get a nonce.

1.1: Embed SqPaymentForm in a static web page

In this step, you add the following components to the index.html page:

• Required CSS and JS references.

• A <div/> with credit card fields.

• A <script/>. The script manages the SqPaymentForm object and user interaction using a JavaScript initializing block and <div/> tags in the form.

1.1.1: Add script references

Open index.html and add the following references in the <head/> section.

<!-- link to the SqPaymentForm library -->
<script type="text/javascript" src="https://js.squareupsandbox.com/v2/paymentform">
</script>

<!-- link to the local custom styles for SqPaymentForm -->
<link rel="stylesheet" type="text/css" href="mysqpaymentform.css">

Note the following about these references:

• js.squareupsandbox.com/v2/paymentform is the Square JavaScript library used in testing the payment form in the v2 Sandbox.

• mysqpaymentform.css is the file provided as part of the project you downloaded.

1.1.2: Add an HTML div

Add the following HTML <div/> in the <body/> section of the same index.html.

   <div id="form-container">
     <div id="sq-card-number"></div>
     <div class="third" id="sq-expiration-date"></div>
     <div class="third" id="sq-cvv"></div>
     <div class="third" id="sq-postal-code"></div>
     <button id="sq-creditcard" class="button-credit-card" onclick="onGetCardNonce(event)">Pay $1.00</button>
   </div> <!-- end #form-container --> 
   <!-- TODO: Add script from step 1.1.3 -->

In the form, note the following:

• Each credit card field is an empty <div/> with an id. SqPaymentForm will replace each <div/> with an input element that runs securely on Square’s domain. This allows the form to take credit card input while keeping your code outside of PCI scope.

• The onclick event handler (onGetCardNonce) calls the SqPaymentForm.requestCardNonce library function to get a nonce.

1.1.3: Add JavaScript to index.html

In this section, you provide code to the HTML page to configure and initialize the SqPaymentForm object. We add the <script/> in the because SqPaymentForm can be initialized only after the DOM is fully loaded.

Copy and paste the following code after the <!-- TODO: Add script from step 1.1.3 --> in index.html:

   <script type="text/javascript">
     // Create and initialize a payment form object
     const paymentForm = new SqPaymentForm({
       // Initialize the payment form elements
       
       //TODO: Replace with your sandbox application ID
       applicationId: "REPLACE_WITH_APPLICATION_ID",
       inputClass: 'sq-input',
       autoBuild: false,
       // Customize the CSS for SqPaymentForm iframe elements
       inputStyles: [{
           fontSize: '16px',
           lineHeight: '24px',
           padding: '16px',
           placeholderColor: '#a0a0a0',
           backgroundColor: 'transparent',
       }],
       // Initialize the credit card placeholders
       cardNumber: {
           elementId: 'sq-card-number',
           placeholder: 'Card Number'
       },
       cvv: {
           elementId: 'sq-cvv',
           placeholder: 'CVV'
       },
       expirationDate: {
           elementId: 'sq-expiration-date',
           placeholder: 'MM/YY'
       },
       postalCode: {
           elementId: 'sq-postal-code',
           placeholder: 'Postal'
       },
       // SqPaymentForm callback functions
       callbacks: {
           /*
           * callback function: cardNonceResponseReceived
           * Triggered when: SqPaymentForm completes a card nonce request
           */
           cardNonceResponseReceived: function (errors, nonce, cardData) {
           if (errors) {
               // Log errors from nonce generation to the browser developer console.
               console.error('Encountered errors:');
               errors.forEach(function (error) {
                   console.error('  ' + error.message);
               });
               alert('Encountered errors, check browser developer console for more details');
               return;
           }
              alert(`The generated nonce is:\n${nonce}`);
              //TODO: Replace alert with code in step 2.1
           }
       }
     });
     //TODO: paste code from step 1.1.4
   </script>

In the JavaScript code, note the following:

• The callback cardNonceResponseReceived alerts the user that a nonce is generated and returned by the SqPaymentForm object. In step 2.1, The nonce will be POSTed to a server-side component to charge the payment source. The server-side component is reviewed in Step 2.

1.1.4: Add javascript to handle "Pay $1.00" button click event “onclick”

In this section, you add a callback function to handle the pay button click event. The event handler calls requestCardNonce to get the payment card nonce from the SqPaymentForm object.

Copy and paste into index.html after //TODO: paste code from step 1.1.4

     //TODO: paste code from step 1.1.5
     // onGetCardNonce is triggered when the "Pay $1.00" button is clicked
     function onGetCardNonce(event) {
       // Don't submit the form until SqPaymentForm returns with a nonce
       event.preventDefault();
       // Request a nonce from the SqPaymentForm object
       paymentForm.requestCardNonce();
     }

1.1.5: Add javascript to build the form

In this section you add JavaScript to force the SqPaymentForm object to render the payment form in the page.

Copy and paste after //TODO: paste code from step 1.1.5

     paymentForm.build();

1.2: Provide your application ID

For SqPaymentForm to load successfully, open index.html and find //TODO: Replace with your sandbox application ID. Provide your Sandbox Application ID. SqPaymentForm requires a valid Application ID to return a nonce.

// TODO: Replace with your sandbox application ID
applicationId = "REPLACE_WITH_APPLICATION_ID";

1.3: Test the payment form and verify the secure token (nonce)

Do the following to test the payment form:

How did this work? (Application Flow Summary)

In this section, you don't perform actions. Instead, the section explains how the code you developed in step 1 works. You can read or skip ahead to step 2 to charge the payment source.

When the page loads, it renders the payment form defined in the index.html file. The page also downloads and executes the SqPaymentForm Javascript library. This is a library that provides the SqPaymentForm object. For more information about the library, see SqPaymentForm data model.

Embedded JavaScript. This code does two things:

• Initializes the SqPaymentForm with configuration fields and callback functions.

  Each credit card input form field requires a corresponding configuration field. For example, the SqPaymentForm initialization defines the card number input as shown in this inputTarget field.

   cardNumber: {
     elementId: 'sq-card-number',
     placeholder: 'Card Number'
   }
  

  It maps the SqPaymentForm.cardNumber configuration field to corresponding form field sq-card-number.

  The SqPaymentForm initialization also includes callback implementations, for example the SqPaymentForm.cardNonceResponseReceived. The callback executes after SqPaymentForm completes a request for a nonce.

• Provides code for the event handler onGetCardNonce that executes after you click Pay $1.00.

After the payment form is built, it replaces DOM elements with iframes. The iframes take the buyer-entered credit card information and call the requestCardNonce function to get a nonce. This allows you to take payments through Square.

After a buyer enters their information in the form and clicks Pay $1.00, the onGetCardNonce event handler executes. This code generates a nonce by calling the SqPaymentForm.requestCardNonce function and passes the nonce back to the client by calling the SqPaymentForm.cardNonceResponseRecieved callback. The client displays an alert box with generated nonce.

Step 2: Charge the Payment Source Using the Nonce

index.html sends the nonce to Server.js by using the fetch API. Server.js uses it to create a payment. This server-side component uses the Square Node.js SDK library to call the Square Payments API to charge the payment source using the nonce. In step 2, you will add the fetch code to index.html and update server.js with your personal access token.

2.1: Add javascript to send the nonce to the backend

In this section, you make a final change to index.html. You will replace the alert that notifies on nonce received with code that actually sends the nonce to server.js.

Copy and paste the following code into index.html in place of //TODO: Replace alert with code in step 2.1.

              fetch('process-payment', {
                method: 'POST',
                headers: {
                  'Accept': 'application/json',
                  'Content-Type': 'application/json'
                },
                body: JSON.stringify({
                  nonce: nonce
                })
              })
              .catch(err => {
                alert('Network error: ' + err);
              })
              .then(response => {
                if (!response.ok) {
                  return response.text().then(errorInfo => Promise.reject(errorInfo));
                }
                return response.text();
              })
              .then(data => {
                console.log(JSON.stringify(data));
                alert('Payment complete successfully!\nCheck browser developer console for more details');
              })
              .catch(err => {
                console.error(err);
                alert('Payment failed to complete!\nCheck browser developer console for more details');
              });

  

2.2: Configure backend with your access token

The JavaScript code in server.js is already complete but it is not set with your sandbox personal access token. In this step, you replace the placeholder with your token.

2.3: Test the payment flow from client to server

This time you will generate a nonce and also charge the payment source using the generated nonce.

Build a single-element payment form (Beta)

The SqPaymentForm library offers two ways to configure a payment form in your website as shown:

• Multi-element payment form. You build the payment form with DOM elements, one for each of the card data item (card number, expiry date, CVV value, and postal code). You map each of the DOM elements to the corresponding SqPaymentForm configuration inputTarget. This is the payment form you built in the preceding walkthrough.

• Build a single-element payment form. The SqPaymentForm library also provides the card configuration field to build a single-element payment form. The single form element can take all the card information. This can simplify coding:

  • Instead of defining the four DOM elements for taking card information you define only one DOM element and map it to the card configuration field.

  • The card configuration field provides a default CSS configuration. For example, you don't need much of the CSS work you did in the preceding exercise. The default style of the single-element form can be customized to conform to payment page styles. See Customize the Appearance of the Single-element Payment Form to learn about styling the single-element form.

  Using the card element is an alternative to building a payment form if you don't need the flexibility of individually placed payment card fields.

Let us update the walkthrough to use the card configuration element. Follow the steps to update files you created in step 1.2, where you added code to embed SqPaymentForm in a static web page.

When you have completed your project code updates to run the single-element payment form, go back to Step 2.3: Test the payment flow from client to server and follow the instructions to re-test your payment form.

Single-element payment form and digital wallet support

The SqPaymentForm object in single-element payment form mode does not support digital wallets. If you want to use a single-element payment form in a payment page along with digital wallets, you can do so by adding a 2nd instance of SqPaymentForm configured with only the digital wallet elements. Then you add callbacks for digital wallet support to the 2nd instance of SqPaymentForm.

Deploy the application to production

In the preceding walkthrough you used the v2 Sandbox environment to test the payment form using a fake credit card number. This section explains how you deploy the application in production. In summary, you do the following:

• Replace sandbox credentials with production credentials

• Update your code to send requests to the production endpoints

• Take payments with a valid credit card. Square will actually charge the card

To deploy the preceding walkthrough in production, do the following:

When you have completed these steps, your app will run in production. If you want to test, you will need to use a real credit card. We recommend you charge a small amount because Square will charge the credit card.