Create CLI application in NodeJS

In this application, I will create a CLI-based application. It means you will interact only with the Node CLI.

Now I am going to make a simple add application to add the number(s). I will also implement error handling within this application.

So let’s start.

Instantiate the readline module:

 var readline = require(‘readline’);

The above module will help us to create an interface for the CLI application.

Instantiate the CLI Module object:

var cli = {};

Now create the CLI functions as:

cli.processInput = function (str) {
str = typeof (str) == ‘string’ && str.trim().length > 0 ? str.trim() : false;
  if (str) {
       var inputs = str.split(‘ ‘);
      if (inputs.length >= 3) {
          var results = 0;
           inputs.some(function (value) {
                  if (!isNaN(value)) {
                        results = results + parseInt(value);
                   }
           })
          console.log(“\x1b[36m”,”Total is :”,results);
          return true;
    } else {
          console.error(“\x1b[31m”,”Error: Too few parameter”);
          return false;
     }
  }
}

Create an init script to start the CLI application:

cli.init = function () {
     /* Send the start message to the console in dark blue. */
     console.log(‘\x1b[33m%s\x1b[0m’, ‘CLI is running’);
    /* Start the interface */
    var _interface = readline.createInterface({
            input: process.stdin,
            output: process.stdout,
            prompt: ‘>’
    })
   /* Create an initial prompt */
   _interface.prompt(); // Will wait for input
  /* Handle each line of input separately. */
  _interface.on(‘line’, function (str) {
  /* Send to input processor. */
  cli.processInput(str);
  /* re-initialize the prompt afterwards. */
   _interface.prompt();
  });
}

Now start the script:

cli.init();

Save the application:
Save this application as cliApp.js

Run the application:

node cliApp.js

Congratulations… your first CLI application in nodeJs has been successfully Created:

Output:

Thanks for reading.