Adding Installment Information in the Product Details Page

FastStore Extending the FastStore API API extensions - Use cases

This guide outlines how you can display available product installment options on your Product Details Page (PDP).

For detailed instructions on API extensions, see the API extensions guide.

Context

You want to display installment details (number, amount, payment system) on the PDP. This feature allows customers to view installment details directly on the product page, supporting their decision-making.

Implementation

Creating GraphQL files

First, you must configure the necessary GraphQL files to retrieve and structure the installment data.

In your store repository, go to the src folder. If you don’t have it, create a graphql folder.
Inside graphql, create the vtex folder.
In the vtex folder, create two other subfolders, resolvers and typeDefs.

For further information on code implementation, see the vtex folder available in the playground.store repository.


_10src  
_10┗ 📂 graphql  
_10    ┗ 📂vtex  
_10        ┣ 📂 resolvers  
_10        ┗ 📂 typeDefs

Defining the types

Now that the file structure is in place, let's define the data structure for our installment information using GraphQL.

In the typeDefs folder, create a product.graphql file to define the schema. Add the following schema definitions:

Installments: Specifies the structure of each installment option. Each installment has properties for:
installmentPaymentSystemName: Name of the payment system used (e.g., Credit Card).
installmentValue: Amount of each installment.
installmentInterest: Interest rate applied per installment.
installmentNumber: Total number of installments offered.
StoreProduct: Type that is being extended to include a new field called availableInstallments. This field is a list of installment objects, representing all the available installment options for the product.

product.graphql


_13type Installments {
_13  installmentPaymentSystemName: String!
_13  installmentValue: Float!
_13  installmentInterest: Float!
_13  installmentNumber: Float!
_13}
_13
_13extend type StoreProduct {
_13  """
_13  Retrieve available installment data extending StoreProduct
_13  """
_13  availableInstallments: [Installments!]!
_13}

Creating resolvers

Now that we've defined the structure of our installment information (GraphQL types), let's create the rationale for retrieving and formatting this information using a resolver function. Resolvers essentially act as gateways between your frontend and backend, processing data requests.

In the resolvers folder, create a product.ts file to handle the installment information rationale. Add the following code.

productResolver: Defines a resolver for the StoreProduct type.
availableInstallments: Retrieves the installment information from the commertialOffer property of the first seller (sellers[0]).
installments.length: Checks if there are any installments (installments.length). If not, an empty array is returned.
The code iterates through each installment and maps it to a new object with the desired properties (installmentPaymentSystemName, installmentValue, etc.).

product.graphql

product.ts


_22import type { StoreProductRoot } from "@faststore/core/api";
_22
_22const productResolver = {
_22  StoreProduct: {
_22    availableInstallments: (root: StoreProductRoot) => {
_22      const installments = root.sellers?.[0]?.commertialOffer?.Installments;
_22
_22      if (!installments.length) {
_22        return [];
_22      }
_22
_22      return installments.map((installment) => ({
_22        installmentPaymentSystemName: installment.PaymentSystemName,
_22        installmentValue: installment.Value,
_22        installmentInterest: installment.InterestRate,
_22        installmentNumber: installment.NumberOfInstallments,
_22      }));
_22    },
_22  },
_22};
_22
_22export default productResolver;

Consolidating resolvers

In the resolvers folder, create an index.ts file to consolidate the resolvers.

The index.ts file exports resolvers by default, acting as a central hub for all your resolver functions.
resolvers:Combines the imported resolver with any other resolvers you might have in your project (represented by the ellipsis ...).

product.graphql

product.ts

index.ts


_10import { default as StoreProductResolver } from "./product";
_10
_10const resolvers = {
_10  ...StoreProductResolver,
_10};
_10
_10export default resolvers;

Using fragments

Now that we've defined the availableInstallments field using GraphQL types and resolvers, we need to specify where this data will be used in your storefront queries. This is achieved through GraphQL fragments.

In the src folder of your store code, create a fragments folder.
In the fragments folder, create the following files:
- ClientProduct.ts: Defines the client-side fragment.
- ServerProduct.ts: Defines the server-side fragment.
In the ClientProduct.ts file, defines the GraphQL fragment for retrieving installment data.

gql: Imported from @faststore/core/api to construct the GraphQL fragment.
ClientProduct: Fragment to indicate it extends the product query.
The fragment defines the specific fields we want to retrieve from the availableInstallments data structure.

product.graphql

product.ts

index.ts

ClientProduct.ts


_14import { gql } from "@faststore/core/api";
_14
_14export const fragment = gql(`
_14  fragment ClientProduct on Query {
_14    product(locator: $locator) {
_14      availableInstallments {
_14        installmentPaymentSystemName
_14        installmentValue
_14        installmentInterest
_14        installmentNumber
_14      }
_14    }
_14  }
_14`);

Adding server-side product fragment for installment details

Add a product fragment focusing on installment details to ensure consistency in data retrieval on the client and server sides. In the ServerProduct.ts file, add the following:

For further details on code implementation, see the fragments folder available in the playground.store repository.

product.graphql

product.ts

index.ts

ClientProduct.ts

ServerProduct.ts


_14import { gql } from "@faststore/core/api";
_14
_14export const fragment = gql(`
_14  fragment ServerProduct on Query {
_14    product(locator: $locator) {
_14      availableInstallments {
_14        installmentPaymentSystemName
_14        installmentValue
_14        installmentInterest
_14        installmentNumber
_14      }
_14    }
_14  }
_14`);

Formatting installment values

For a more user-friendly display, you can format the installment values to include currency symbols and proper locale formatting.

In the src folder of your store code, create a utils folder.
Inside utils, create the priceFormatter.ts file and add the following:

FaststoreConfig: Imported to access the current store's locale and currency settings.
priceFormatter: This function takes a numeric value and formats it according to the store's locale and currency.

For further details on code implementation, see the utils folder available in the playground.store repository.

product.graphql

product.ts

index.ts

ClientProduct.ts

ServerProduct.ts

priceFormatter.ts


_10import FaststoreConfig from "../../faststore.config.js";
_10
_10export const priceFormatter = (value: number) => {
_10  return value.toLocaleString(FaststoreConfig.session.locale, {
_10    style: "currency",
_10    currency: FaststoreConfig.session.currency.code,
_10  });
_10};

Creating a new component with installments

Now that we've established the rationale for retrieving installment data, let's create a new component to display this information alongside the buy button on the PDP.

In the src/components folder, create two new folders:
- BuyButtonWithDetails: Keeps the component for our enhanced buy button with installment details.
- sections/CustomProductDetails: Keeps the rationale for overriding the default PDP buy button component.
Inside the BuyButtonWithDetails folder, create two new files:
- BuyButtonWithDetails.tsx
- buy-button-with-details.module.scss
Inside BuyButtonWithDetails.tsx, add the following code.

priceFormatter: Format installment values.
styles: Stylesheet for the BuyButtonWithDeatils imported from the .scss file.
usePDP: Hook to retrieve the PDP context containing product and extension data.
We conditionally display the first installment option if it's interest-free (you can modify this to show all installments).
The component renders a section containing the installment information and the buy button.

product.graphql

product.ts

index.ts

ClientProduct.ts

ServerProduct.ts

priceFormatter.ts

BuyButtonWithDetails.tsx


_32import { usePDP } from "@faststore/core";
_32import { Button as UIButton, ButtonProps } from "@faststore/ui";
_32import { priceFormatter } from "../../utils/priceFormatter";
_32
_32import styles from "./buy-button-with-details.module.scss";
_32
_32export function BuyButtonWithDetails(props: ButtonProps) {
_32  const context = usePDP();
_32
_32  const installment = context?.data?.product?.availableInstallments[0];
_32  const interestFree = installment.installmentInterest === 0 ?? false;
_32
_32  return (
_32    <section className={styles.buyButtonWithDetails}>
_32      {interestFree && (
_32        <span>
_32          {`${installment.installmentNumber} interest-free installment(s)`}
_32          <br />
_32          {`of ${priceFormatter(installment.installmentValue)} with ${
_32            installment.installmentPaymentSystemName
_32          }`}
_32        </span>
_32      )}
_32
_32      <UIButton {...props} variant="primary">
_32        Buy Button
_32      </UIButton>
_32    </section>
_32  );
_32}
_32
_32export default BuyButtonWithDetails;

Creating a stylesheet for the component

Inside buy-button-with-details.module.scss, add the code below. The stylesheet styles the component using SCSS. It defines styles for the installment information container and the buy button itself.

product.graphql

product.ts

index.ts

ClientProduct.ts

ServerProduct.ts

priceFormatter.ts

BuyButtonWithDetails.tsx

buy-button-with-details.module.scss


_16.buyButtonWithDetails {
_16  > span {
_16    display: flex;
_16    justify-content: center;
_16    margin-bottom: var(--fs-spacing-4);
_16    text-align: center;
_16    font-size: var(--fs-text-size-1);
_16  }
_16
_16  [data-fs-button] {
_16    width: 100%;
_16    [data-fs-button-wrapper] {
_16      background-color: var(--fs-color-neutral-7);
_16    }
_16  }
_16}

Creating a custom section

By including the CustomProductDetails section in the PDP, you replace the default buy button component with your enhanced BuyButtonWithDetails component, which displays both the buy button and the installment information.

In the CustomProductDetails folder , create the CustomProductDetails.tsx and add the following code.

For further details on code implementation, see the utils folder available in the playground.store repository.

product.graphql

product.ts

index.ts

ClientProduct.ts

ServerProduct.ts

priceFormatter.ts

BuyButtonWithDetails.tsx

buy-button-with-details.module.scss

CustomProductDetails.tsx


_11import { getOverriddenSection, ProductDetailsSection } from "@faststore/core";
_11import { BuyButtonWithDetails } from "../../BuyButtonWithDetails/BuyButtonWithDetails";
_11
_11const CustomProductDetails = getOverriddenSection({
_11  Section: ProductDetailsSection,
_11  components: {
_11    BuyButton: { Component: BuyButtonWithDetails },
_11  },
_11});
_11
_11export default CustomProductDetails;

Creating GraphQL files

First, you must configure the necessary GraphQL files to retrieve and structure the installment data.

In your store repository, go to the src folder. If you don’t have it, create a graphql folder.
Inside graphql, create the vtex folder.
In the vtex folder, create two other subfolders, resolvers and typeDefs.

For further information on code implementation, see the vtex folder available in the playground.store repository.

Defining the types

Now that the file structure is in place, let's define the data structure for our installment information using GraphQL.

In the typeDefs folder, create a product.graphql file to define the schema. Add the following schema definitions:

Installments: Specifies the structure of each installment option. Each installment has properties for:
installmentPaymentSystemName: Name of the payment system used (e.g., Credit Card).
installmentValue: Amount of each installment.
installmentInterest: Interest rate applied per installment.
installmentNumber: Total number of installments offered.
StoreProduct: Type that is being extended to include a new field called availableInstallments. This field is a list of installment objects, representing all the available installment options for the product.

Creating resolvers

In the resolvers folder, create a product.ts file to handle the installment information rationale. Add the following code.

productResolver: Defines a resolver for the StoreProduct type.
availableInstallments: Retrieves the installment information from the commertialOffer property of the first seller (sellers[0]).
installments.length: Checks if there are any installments (installments.length). If not, an empty array is returned.
The code iterates through each installment and maps it to a new object with the desired properties (installmentPaymentSystemName, installmentValue, etc.).

Consolidating resolvers

In the resolvers folder, create an index.ts file to consolidate the resolvers.

The index.ts file exports resolvers by default, acting as a central hub for all your resolver functions.
resolvers:Combines the imported resolver with any other resolvers you might have in your project (represented by the ellipsis ...).

Using fragments

In the src folder of your store code, create a fragments folder.
In the fragments folder, create the following files:
- ClientProduct.ts: Defines the client-side fragment.
- ServerProduct.ts: Defines the server-side fragment.
In the ClientProduct.ts file, defines the GraphQL fragment for retrieving installment data.

gql: Imported from @faststore/core/api to construct the GraphQL fragment.
ClientProduct: Fragment to indicate it extends the product query.
The fragment defines the specific fields we want to retrieve from the availableInstallments data structure.

Adding server-side product fragment for installment details

Add a product fragment focusing on installment details to ensure consistency in data retrieval on the client and server sides. In the ServerProduct.ts file, add the following:

For further details on code implementation, see the fragments folder available in the playground.store repository.

Formatting installment values

For a more user-friendly display, you can format the installment values to include currency symbols and proper locale formatting.

In the src folder of your store code, create a utils folder.
Inside utils, create the priceFormatter.ts file and add the following:

FaststoreConfig: Imported to access the current store's locale and currency settings.
priceFormatter: This function takes a numeric value and formats it according to the store's locale and currency.

For further details on code implementation, see the utils folder available in the playground.store repository.

Creating a new component with installments

Now that we've established the rationale for retrieving installment data, let's create a new component to display this information alongside the buy button on the PDP.

In the src/components folder, create two new folders:
- BuyButtonWithDetails: Keeps the component for our enhanced buy button with installment details.
- sections/CustomProductDetails: Keeps the rationale for overriding the default PDP buy button component.
Inside the BuyButtonWithDetails folder, create two new files:
- BuyButtonWithDetails.tsx
- buy-button-with-details.module.scss
Inside BuyButtonWithDetails.tsx, add the following code.

priceFormatter: Format installment values.
styles: Stylesheet for the BuyButtonWithDeatils imported from the .scss file.
usePDP: Hook to retrieve the PDP context containing product and extension data.
We conditionally display the first installment option if it's interest-free (you can modify this to show all installments).
The component renders a section containing the installment information and the buy button.

Creating a stylesheet for the component

Creating a custom section

In the CustomProductDetails folder , create the CustomProductDetails.tsx and add the following code.

For further details on code implementation, see the utils folder available in the playground.store repository.


_10src  
_10┗ 📂 graphql  
_10    ┗ 📂vtex  
_10        ┣ 📂 resolvers  
_10        ┗ 📂 typeDefs

Results

Once you have set your development mode, you can view changes locally by accessing a PDP, such as https://localhost:3000/adidas-mens-performance-polo-green-night-99984111/p, and you will see the installment option for the product.

Before

The PDP before adding the installment:

${"base64":" ","img":{"width":948,"height":571,"type":"png","mime":"image/png","wUnits":"px","hUnits":"px","length":215607,"url":"https://vtexhelp.vtexassets.com/assets/docs/src/before-installment___c06c92a26445e0dc97a33981f893358e.png"}}$

After

After applying the installment option, the information will become available above the Buy Button:

${"base64":" ","img":{"width":929,"height":676,"type":"png","mime":"image/png","wUnits":"px","hUnits":"px","length":240060,"url":"https://vtexhelp.vtexassets.com/assets/docs/src/after-installment___77227bfcffcf9a25800effe9790100e1.png"}}$