![How to set up Scheduled Functions with NodeJs, Express and Node-Cron](/assets/pexels-pixabay-273153.jpg "How to Setup Scheduled Functions with NodeJs, Express and Node-Cron")

## Step 1: Create a [NodeJs](https://nodejs.org/en/) application.

Initialize a new app with npm and install the [Express](http://expressjs.com/) package. Make sure NodeJs is installed on your machine. 

   \- npm init

   \- npm i express

## Step 2: Set up the Express server

   \- Create the **app.js** file (note that some people prefer to call this file **server.js**)
   
   \- Configure the port and set up the listener

```javascript
const express = require("express");
const app = express();
app.set("port", process.env.PORT || 3000);

app.listen(app.get("port"), () => {
  console.log("Express server listening on port " + app.get("port"));
});
```

## Step 3: Add the [node-cron](https://www.npmjs.com/package/node-cron) npm package to the application

   \- npm i node-cron

## Step 4: Set up a folder for your scheduled jobs

   \- Create a folder called "scheduledFunctions" or similar

## Step 5: Define the logic to run your scheduled jobs

   \- In the folder you just set up, create a file to hold your scheduled function logic. You can also use different files for each task if you prefer.

   \- Configure scheduled logic

   ```javascript
   const CronJob = require("node-cron");

   exports.initScheduledJobs = () => {
     const scheduledJobFunction = CronJob.schedule("*/5 * * * *", () => {
       console.log("I'm executed on a schedule!");
       // Add your custom logic here
     });

     scheduledJobFunction.start();
   }
   ```

   The execution frequency of your custom function is defined as the first argument to the Cron.schedule function. Note that this argument is written as a Cron Schedule Expression or [crontab](https://en.wikipedia.org/wiki/Cron). I find [Crontab Guru](https://crontab.guru/) a really useful resource to play around and get comfortable with schedule expressions so you can easily set up your own.

## Step 6: Configure the Express app to initialise and run the job schedules

   \- In the **app.js** file add a call to the init function(s) from your scheduled file(s).
   
   ```javascript
   const express = require("express");
   // DEFINE the path to your scheduled function(s)
   const scheduledFunctions = require('./scheduledFunctions');
   const app = express();
   app.set("port", process.env.PORT || 3000);

   // ADD CALL to execute your function(s)
   scheduledFunctions.initScheduledJobs();

   app.listen(app.get("port"), () => {
     console.log("Express server listening on port " + app.get("port"));
   });
   ```

   Start the app to generate the functions and their schedules in the Cron scheduler. Your custom logic will be executed to schedule as long as the app is running.

Building an API with NodeJs and Express is always a key building block of any full stack application. In conjunction with managing user requests, a NodeJs API application can also help maintain database integrity by performing scheduled maintenance checks to ensure everything remains in solid working order.