---
title: "Configure the Basic I/O function"
url: https://docs.catalyst.zoho.com/en/tutorials/hosted-login-app/nodejs/configure-function/
description: "Create a simple Basic or React application using the features of Catalyst Hosted Authentication that provides user sign-up, application login, password reset, and implements sign-in using prevalent federated identity providers."
last_updated: 2025-11-19T15:07:41Z
service: All Services
type: tutorial
related_links:
  - name: "Basic I/O Functions"
    url: /en/serverless/help/functions/basic-io/
  - name: "Functions Directory Structure"
    url: /en/cli/v1/project-directory-structure/functions-directory
---

# Configure the Function

Now, we will begin coding the authorization portal application by configuring the function component.

The [function’s directory](https://docs.catalyst.zoho.com/en/cli/v1/project-directory-structure/functions-directory), (`functions/authorization_portal_function`), contains:

* The `index.js` main function file
* The `catalyst-config.json` configuration file
* Node modules
* [`package.json`](https://docs.npmjs.com/files/package.json) and [`package-lock.json`](https://docs.npmjs.com/configuring-npm/package-lock-json.html) dependency files

You will be adding code in the `index.js` file.

The Basic I/O function contains the following functionalities:

* The end-user's details will provided as a JSON input to the *Custom User Validation* function.
* The function is coded to implement a custom logic based upon which the end-user will either be authenticated or denied.

> **Note:** For the purpose of this tutorial, we have coded a logic for the Custom User Validation function where if the user's email provider is anyone other than Zylker Technology (`@zylker.com`) the end-user will not be able to sign up to the application. You can either use the same or code a logic of your preference.

Now, let’s begin coding the Basic I/O function.

Copy the code given below and paste it in the `index.js` file in the `functions/authorization_portal_function` directory of your project, and save the file. You can use any IDE of your choice to work with the application’s files.

> **Note:** Please go through the code in this section to make sure you fully understand it.

**index.js**

```javascript
const catalyst = require("zcatalyst-sdk-node");
module.exports = (context, basicIO) => {
  const catalystApp = catalyst.initialize(context);
  const requestDetails = catalystApp
    .userManagement()
    .getSignupValidationRequest(basicIO);
  if (requestDetails) {
    if (requestDetails.user_details.email_id.includes("@zylker.com")) {
      // The actions that occur in the event of a successful authentication can be customized
      basicIO.write(
        JSON.stringify({
          status: "success",
          user_details: {
            first_name: requestDetails.user_details.first_name,
            last_name: requestDetails.user_details.last_name,
            email_id: requestDetails.user_details.email_id,
            role_identifier: "App User", // If you want to override the default role, you can specify the role id/name here.
            org_id: "", // If you are providing the Org ID, make sure it is copied exactly from the console.
          },
        })
      );
    } else {
      // The user has failed authentication
      basicIO.write(
        JSON.stringify({
          status: "failure",
        })
      );
    }
  }
  context.close();
};

```

> **Note:** You can also use this [SDK](https://docs.catalyst.zoho.com/en/sdk/nodejs/v2/cloud-scale/authentication/custom-user-validation/) to code your own custom logic instead of the one implemented above.

The function directory is now configured. We can now proceed to configuring the client directory.