 /*
TODO 1: 
A. Define a function with identifier getUsername
B. Inside this function, print the message "Getting username..." to the console
C. Write a setTimeout() function with a delay of 3 seconds to mock getting the username from the user
(you need to assign value 'srishti' to the username inside the setTimeout() function)
D. Print the username to the console, as shown in the Problem Statement
E. Call the callback function validateUsername() while passing in the username as the argument to it
*/

let username;
const getUsername = (validateUsername) => {
    console.log("Getting username...");
    setTimeout(()=>{
        username = 'srishti';
        console.log("Username = "+username);
        validateUsername(username);
    },3000);
};


/*
TODO 2: 
A. Define a function with identifier validateUsername
B. Inside this function, print the message "Validating username..." to the console
C. Validate the username passed to this function as the argument
(A username is VALID when it is not undefined and null and an empty string)
D. If the username is valid, print the message "Valid Username!" on the console and call the callback function passed in the argument
E. If the username is not valid, print the message "Invalid Username! Please try again!"
*/

const validateUsername = (username,cb) => {
    console.log("Validating username...");
    if(username !== null && username !== undefined && username !== ""){
        console.log("Valid Username!");
        cb();
    }else{
        console.log("Invalid Username! Please try again");
    }
}

/*
TODO 3: 
A. Define a function with identifier getPassword
B. Inside this function, print the message "Getting password..." to the console
C. Write a setTimeout() function with a delay of 3 seconds to mock getting the password from user
(you need to assign value 'upgrad' to the password inside the setTimeout() function)
D. Print the password to the console, as shown in the Problem Statement
E. Call the callback function validatePassword() while passing in the password as the argument to it
*/

let password;
const getPassword = (validatePassword) => {
    console.log("Getting password...");
    setTimeout(()=>{
        password = 'upgrad';
        console.log("password = "+password);
        validatePassword(password);
    },3000);
};

/*
TODO 4: 
A. Define a function with identifier validatePassword
B. Inside this function, print the message "Validating password..." to the console
C. Validate the password passed to this function as the argument
(A password is VALID when it is not undefined and null and an empty string)
D. If the password is valid, print the message "Valid Password!" on the console and call the callback function passed in the argument
E. If the password is not valid, print the message "Invalid Password! Please try again!"
*/

const validatePassword = (password,cb) => {
    console.log("Validating password...");
    if(password !== null && password !== undefined && password !== ""){
        console.log("Valid password!");
        cb();
    }else{
        console.log("Invalid password!");
    }
}

/*
TODO 5: Define a function with identifier done which logs the message "BOTH VALID!" on the console
*/

const done = () => {
    console.log("BOTH VALID!");
}


/*
TODO 6: 
A. Define a function with identifier login
B. Inside the login() function, call the getUsername() function
C. Pass validateUsername() function with username argument as the callback function inside the getUsername() function
D. Pass getPassword() function as the callback function inside the validateUsername() function
E. Pass the validatePassword() function with password argument as the callback function inside the getPassword() function
F. Pass the done() function as the callback function inside the validatePassword() function
*/

const login = () => {
    getUsername(username=>validateUsername(username,getPassword(password=>validatePassword(password,done))))
}

login();

created 3 years ago

Javascript Online Compiler

Write, Run & Share Javascript code online using OneCompiler's JS online compiler for free. It's one of the robust, feature-rich online compilers for Javascript language. Getting started with the OneCompiler's Javascript editor is easy and fast. The editor shows sample boilerplate code when you choose language as Javascript and start coding.

About Javascript

Javascript(JS) is a object-oriented programming language which adhere to ECMA Script Standards. Javascript is required to design the behaviour of the web pages.

Key Features

Open-source
Just-in-time compiled language
Embedded along with HTML and makes web pages alive
Originally named as LiveScript.
Executable in both browser and server which has Javascript engines like V8(chrome), SpiderMonkey(Firefox) etc.

Syntax help

STDIN Example

var readline = require('readline');
var rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  terminal: false
});

rl.on('line', function(line){
    console.log("Hello, " + line);
});

variable declaration

Keyword	Description	Scope
var	Var is used to declare variables(old way of declaring variables)	Function or global scope
let	let is also used to declare variables(new way)	Global or block Scope
const	const is used to declare const values. Once the value is assigned, it can not be modified	Global or block Scope

Backtick Strings

Interpolation

let greetings = `Hello ${name}`

Multi line Strings

const msg = `
hello
world!
`

Arrays

An array is a collection of items or values.

Syntax:

let arrayName = [value1, value2,..etc];
// or
let arrayName = new Array("value1","value2",..etc);

Example:

let mobiles = ["iPhone", "Samsung", "Pixel"];

// accessing an array
console.log(mobiles[0]);

// changing an array element
mobiles[3] = "Nokia";

Arrow functions

Arrow Functions helps developers to write code in concise way, it’s introduced in ES6.
Arrow functions can be written in multiple ways. Below are couple of ways to use arrow function but it can be written in many other ways as well.

Syntax:

() => expression

Example:

const numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
const squaresOfEvenNumbers = numbers.filter(ele => ele % 2 == 0)
                                    .map(ele => ele ** 2);
console.log(squaresOfEvenNumbers);

De-structuring

Arrays

let [firstName, lastName] = ['Foo', 'Bar']

Objects

let {firstName, lastName} = {
  firstName: 'Foo',
  lastName: 'Bar'
}

rest(...) operator

 const {
    title,
    firstName,
    lastName,
    ...rest
  } = record;

Spread(...) operator

//Object spread
const post = {
  ...options,
  type: "new"
}
//array spread
const users = [
  ...adminUsers,
  ...normalUsers
]

Functions

function greetings({ name = 'Foo' } = {}) { //Defaulting name to Foo
  console.log(`Hello ${name}!`);
}
 
greet() // Hello Foo
greet({ name: 'Bar' }) // Hi Bar

Loops

1. If:

IF is used to execute a block of code based on a condition.

Syntax

if(condition){
    // code
}

2. If-Else:

Else part is used to execute the block of code when the condition fails.

Syntax

if(condition){
    // code
} else {
    // code
}

3. Switch:

Switch is used to replace nested If-Else statements.

Syntax

switch(condition){
    case 'value1' :
        //code
        [break;]
    case 'value2' :
        //code
        [break;]
    .......
    default :
        //code
        [break;]
}

4. For

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
//code  
}

5. While

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
  // code 
}

6. Do-While

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
  // code 
} while (condition);

Classes

ES6 introduced classes along with OOPS concepts in JS. Class is similar to a function which you can think like kind of template which will get called when ever you initialize class.

Syntax:

class className {
  constructor() { ... } //Mandatory Class method
  method1() { ... }
  method2() { ... }
  ...
}

Example:

class Mobile {
  constructor(model) {
    this.name = model;
  }
}

mbl = new Mobile("iPhone");