---
title: "Configure the functions directory"
url: https://docs.catalyst.zoho.com/en/tutorials/todo-list/nodejs/configure-function/
description: "Build a Basic, React, or Angular to-do list web application using Catalyst Advanced I/O Function and Catalyst Data Store that enables you to note down tasks and delete them after they are done."
last_updated: 2026-08-17T12:16:04Z
service: All Services
type: tutorial
related_links:
  - 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

Next, we will begin coding the to-do list application by configuring the function component.

The [function's directory](https://docs.catalyst.zoho.com/en/cli/v1/project-directory-structure/functions-directory), `functions/to\_do\_list\_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 three APIs in the Advanced I/O function that handle the routing between the server and the Data Store are:

* **GET /todo:** To obtain the to-do list items from the _TodoItems_ table in the Data Store
* **POST /todo:** To create and save a new list item in the Data Store
* **DELETE /todo:** To delete a list item from the Data Store

#### Install Express Framework for Node.js

We will need to use the [Express framework](https://expressjs.com/) to perform routing operations. 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/to\_do\_list\_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_to_node_express_install](https://catalyst-docs-development.zohostratus.in/images/tutorials/todo-list/catalyst_to_node_express_install.webp) 

This information will also be updated in the `package.json` file.

![catalyst_todo_package_json](https://catalyst-docs-development.zohostratus.in/images/tutorials/todo-list/catalyst_todo_package_json.webp)

Next, let's add the code in the function file. Copy the Node.js code and paste it in `index.js` in the `functions/to\_do\_list\_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 given in this section to ensure you fully understand it. We will discuss the architecture of the function and the client in the next section.

**index.js**

```javascript
const express = require('express');
const catalystSDK = require('zcatalyst-sdk-node');
const app = express();
app.use(express.json());
app.use((req, res, next) => {
const catalyst = catalystSDK.initialize(req);
res.locals.catalyst = catalyst;
next();
});
//GET API. Get existing tasks if any from the server.
app.get('/all', async (req, res) => {
try {
const { catalyst } = res.locals;
const page = parseInt(req.query.page);
const perPage = parseInt(req.query.perPage);
const zcql = catalyst.zcql();
const hasMore = await zcql
.executeZCQLQuery(`SELECT COUNT(ROWID) FROM TodoItems`)
.then((rows) => parseInt(rows[0].TodoItems.ROWID) > page * perPage);
const todoItems = await zcql
.executeZCQLQuery(
`SELECT ROWID,Notes FROM TodoItems LIMIT ${
(page - 1) * perPage + 1
},${perPage}`
)
.then((rows) =>
rows.map((row) => ({
id: row.TodoItems.ROWID,
notes: row.TodoItems.Notes
}))
);
res.status(200).send({
status: 'success',
data: {
todoItems,
hasMore
}
});
} catch (err) {
console.log(err);
res.status(500).send({
status: 'failure',
message: "We're unable to process the request."
});
}
});
// POST API. Contains the logic to create a task
app.post('/add', async (req, res) => {
try {
const { notes } = req.body;
const { catalyst } = res.locals;
const table = catalyst.datastore().table('TodoItems');
const { ROWID: id } = await table.insertRow({
Notes:notes
});
res.status(200).send({
status: 'success',
data: {
todoItem: {
id,
notes
}
}
});
} catch (err) {
console.log(err);
res.status(500).send({
status: 'failure',
message: "We're unable to process the request."
});
}
});
// DELETE API. Contains the logic to delete a task.
app.delete('/:ROWID', async (req, res) => {
try {
const { ROWID } = req.params;
const { catalyst } = res.locals;
const table = catalyst.datastore().table('TodoItems');
await table.deleteRow(ROWID);
res.status(200).send({
status: 'success',
data: {
todoItem: {
id: ROWID
}
}
});
} catch (err) {
console.log(err);
res.status(500).send({
status: 'failure',
message: "We're unable to process the request."
});
}
});
module.exports = app;

```

The functions directory is now configured.