---
title: "Configure the Advanced I/O function"
url: https://docs.catalyst.zoho.com/en/tutorials/payslip-generator-app/nodejs/configure-function/
description: "Build a basic web app that uses Catalyst components to generate a PDF document from a dynamic custom payslip template, and email the generated document to the end-user."
last_updated: 2026-08-17T12:16:04Z
service: All Services
type: tutorial
related_links:
  - name: "Functions"
    url: /en/serverless/help/functions/introduction/
  - name: "Advanced I/O Functions"
    url: /en/serverless/help/functions/advanced-io/
  - name: "Functions Directory Structure"
    url: /en/cli/v1/project-directory-structure/functions-directory/
---

# Configure the Advanced I/O Function

Now, we will begin coding the payslip generator application by configuring the function component.

The [function’s directory](https://docs.catalyst.zoho.com/en/cli/v1/project-directory-structure/functions-directory), `functions/payslip_generator_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 Advanced I/O function contains the following functionalities:
* Triggers the [PDF & Screenshot SDK](https://docs.catalyst.zoho.com/en/sdk/nodejs/v2/smartbrowz/generate-pdfnscreenshot/#generate-visual-documents-using-template) to run a headless browser where we render the inputted details onto the template and generate a PDF document.

* Triggers the [Send Mail SDK](https://docs.catalyst.zoho.com/en/sdk/nodejs/v2/cloud-scale/mail/send-email/) to attach the PDF document and send it via email from within the application.

### Install Express Framework for Node.js

We will be using the [Express framework](https://expressjs.com/) to code the Advanced I/O function. To import the Express package in your function’s code, you must install the Express dependency in your system.

To install `Express.js` in your local machine, navigate to the function’s home directory (`functions/payslip_generator_function`) in your terminal and execute the following command:

```sh
npm install express --save
```

This will install the Express module and save the dependencies.
![catalyst_payslip_express_install](https://catalyst-docs-development.zohostratus.in/images/tutorials/payslip-generator/catalyst_payslip_express_install.webp)

This information will also be updated in the `package.json` file.
![catalyst_payslip_package_json](https://catalyst-docs-development.zohostratus.in/images/tutorials/payslip-generator/catalyst_payslip_package_json.webp)

Now, let's begin coding the Advanced I/O function.

Copy the code given below and paste it in the `index.js` in the `functions/payslip_generator_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.

* Ensure you have provided your **Template ID** in line **33**, and the configured **email ID** in line **68**.

**index.js**

```javascript
'use strict'
const express = require('express')
const catalyst = require('zcatalyst-sdk-node')
const fs = require('fs')
const app = express()
const os = require('os')
const path = require('path')
app.use(express.json())
app.post('/generatepayslip', async (req, res) => {
  try {
    const catalystApp = catalyst.initialize(req)
    const smartbrowz = catalystApp.smartbrowz()
    if (!req.body) {
      throw new Error('Request body is empty')
    }
    const {
      employeeName,
      employeeEmail,
      employeeId,
      designation,
      basicSalary,
      allowances,
      deductions,
      paymentMethod
    } = req.body
    const date = new Date()
    const currentMonth = date.toLocaleString('default', { month: 'long' })
    const currentYear = date.getFullYear()
    const filepath = path.join(os.tmpdir(), '/payslip.pdf')
    // Generate output from template
    await smartbrowz
      .generateFromTemplate('xxxxxxxx12345', // Provide your Template ID
        {
        // Data to be passed to the template retrieved from the client
          template_data: {
            company: 'Zylker Technologies',
            employeeName,
            employeeId,
            designation,
            basicSalary,
            allowances,
            deductions,
            totalEarnings:
            parseFloat(basicSalary) + parseFloat(allowances),
            netSalary:
            parseFloat(basicSalary) +
            parseFloat(allowances) -
            parseFloat(deductions),
            paymentMethod,
            month: currentMonth,
            year: currentYear
          }
        })
      .then((inputStream) => {
        return new Promise((resolve, reject) => {
          inputStream
            .pipe(fs.createWriteStream(filepath))
            .on('close', resolve)
            .on('error', reject)
        })
      }).catch((err) => {
        throw err
      })
    await catalystApp
      .email()
      .sendMail({
        from_email: 'emmy@zylker.com', // Provide your email ID configured in the Console
        to_email: [employeeEmail],
        html_mode: true,
        subject: `Payslip for the month of ${currentMonth} ${currentYear}`,
        content: `Hello ${employeeName}, Your payslip for ${currentMonth} ${currentYear} has been issued. You can find your payslip attached with this email. Cheers,Zylker`,
        attachments: [fs.createReadStream(filepath)] // create a file stream for the file attachment
      })
      .then((row) => {
        res.status(200).send('Payslip generated and sent to Employee email')
      })
      .catch((err) => {
        throw err
      })
  } catch (error) {
    console.log(error)
    res.status(500).send(error)
  }
})
module.exports = app

```

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