User Interaction in CLI programming: readlineSync

Interacting with user input in CLI is much different than GUI. In a CLI app you need to read the user-input using a node package. One such package is readline-sync. It allows the interaction of user with CLI through console.

 How to use readlineSync in your code:

• First initialize npm(node package manager) in your repo -

            npm init     //Some online editor such as repl etc. have this pre-initialized

• Install the readline package from npm in your repo/folder -

            npm install readline-sync     //Some editors automatically execute this part even without mention

• Require the readline-sync module in your code -

            var readlineSync = require('readline-sync');

• Now this readlineSync is ready to be used and perform different functions in your code.

Different uses of readlineSync :

//Simply Taking user Input and displaying it

var username = readlineSync.question("Please tell us your name.");

console.log("Hi"+username);

OUTPUT:

//Acting to user Key Input through readlineSync and KeyIN

if(readlineSync.keyInYN("Do you want to proceed?")) {

console.log("Installing Now...");

} else {

console.log("Searching for other modules!");

}

OUTPUT:

//Hiding user input for readline through hideEchoBack

var username = readlineSync.question("Please tell us your name.");

console.log("Hi"+username);

var favFood = readlineSync.question("Please enter your password:",{

hideEchoBack:true

});

console.log("Thanks for Signing In");

OUTPUT:

//Asking the user to choose input from a list

var readlineSync = require('readline-sync'),

foodItems = ['jalebi','fafda','khicdi','dosa','dhokla'],

index = readlineSync.keyInSelect(foodItems,'Which Item?');

console.log("You will eat "+foodItems[index]+" today");

OUTPUT:

//handle user commands repeatedly similar to as shell interface handling

readlineSync.promptCLLoop({

add:function(target,into) {

console.log(target + " is added to " + into);

},

remove:function(target) {

console.log(target + " is removed.");

},

bye:function() {return true;}

});

console.log("Exited");

OUTPUT:

Apart from these, there are many other functions that can be performed through readlineSync. Go the official Docs of the readline module.