100-wowprogrammers-JS-Questions

@wowprogrogrammers JS Practice Questions Set

WOW Set 1:

Assignments

1.1: Write a code to check difference between null and undefined data type. Also check their type using typeof.

1.2: Which type of variables (var, let or const) must be initialized at the time of declaration?

1.3: Guess the Output and Explain Why?

let languages = 'java javaScript python cSharp';

let result = languages.lastIndexOf('S');

console.log(result);

1.4: Guess the Output and Explain Why?

let variable = 'hello programmers';

let result = Number(variable);

console.log(result);

1.5: Guess the Output and Explain Why?

let num1 = 32;

let num2 = '32';

let result1 = num1 !== num2;

let result2 = num1 != num2;

console.log(result1, result2);

1.6: Guess the Output and explain Why?

let str = 'Hello Programmers';

let result = str.includes('r');

console.log(result);

1.7: Guess the Output and Explain Why?

let num1 = 2;

let num2 = 5;

let result = num1 ** num2 * 2;

console.log(result);

1.8: Guess the Output and Explain Why?

let num1 = [1, 2, 4, 5];

let num2 = [6, 5, 8, 0];

let result = num1.concat(num2);

console.log(result);

1.9: Guess the Output and Explain Why?

let a = 5;

let b = 7;

let c = 8;

let result = a < b > c;

console.log(result);

1.10: If your State is split into four equal parts such that in each part there are 1/4 number of people live. You have to find how many people would live in each part? which operators will you use ?

WOW Set 2:

Assignments:

2.1: Guess the Output And Explain Why?

let i = 4;

for (let j = 0; i < 10; i++) {
  if (j === 1 || i === 6) {
    continue;
  } else {
    console.log(i, j);

    if (i === 7) {
      break;
    }
  }
}

2.2: Guess the Output and Explain Why?

let i = 0;

for (i; i < 5; i++) {
  console.log(i);
}

2.3: Write a simple Program in which You have to print first 10 numbers in descending order (10...1)?

2.4: Lets say John is looking a new country to live in. He want to live in a country that speaks English, has less than 10 million people. One of the food option between these two must present Spanish food OR English food.

Write an if/else if statement to help john figure out Your country is right for him?

2.5: Guess the Output And Explain Why?

for (let i = 0; i < 10; i++) {
  console.log(i);
}

console.log(i);

2.6: use nested-if statement to check your age>18

than check your height height > 5.10.

If both true show any message(I can sit in exam) in the console?

2.7: Create two variables grade and passingYear.Check if your grade == "A" and passingYear < 2020 with the help of ternary operator(Not allowed to use any logical operator).If both condition true print on console Qualify. Otherwise Fail

WOW Set 3:

Assignments

3.1: Create a function Declaration called describeYourState Which take three parameters Population, traditional food and historical place. Based on this input function should return a String with this format.

My state population is ** Its traditional food is ** and historical place name is ___

3.2: Create a function expression which does the exact same thing as defined in Question 1

3.3: Create function addition which takes two numbers as an argument And return the result of sum of two numbers

Important Note: In the function call you are not passing any parameter. You can modify function to achieve this.

Example;

function addition(num1, num2) {
  return num1 + num2;
}
console.log(addition()); //You are not allowed to modify this line any more

3.4: Identify which type of value passed below into the function greet(). What will be the return value of greet ?

let person = {
  name: 'john',

  age: 25,
};

function greet(person) {
  person.name = `Mr ${person.name}`;

  return `Welcome ${person.name}`;
}

greet(person);

3.5: Create higher order function named as transformer which take string and firstUpperCaseWord function as an arguments. firstUpperCaseWord is function which make first word UpperCase from a given String.

3.6: create function which will display Your name after every 5 seconds

input

let  yourName  =  "john";
output

"john"  after  5  second

"john"  after  5  second

"john"  after  5  second

"john"  after  5  second

.

.

.

and  so  on.

3.7: Guess the Output And Explain Why?

let arrowFunction = (name = 'Coders') => {
  `Welcome ${name}`;
};

console.log(arrowFunction('Programmers'));

3.8: Create a JavaScript Function to find the area of a triangle where lengths of the three of its sides are 5, 6, 7. : Area = Square root of√s(s - a)(s - b)(s - c) where s is half the perimeter, or (a + b + c)/2.

input: area_of_triangle(5, 6, 7);

output: 14.69;

3.9: Create a JavaScript Function to capitalize the first letter of each word of a given string.

input: capitalize('we are the champions');

output: 'We Are The Champions';

WOW Set 4:

Assignments

4.1: Guess the Output And Explain ?

console.log(Math.round(Math.random() * 10));

4.2: Create an object called country for a country of your choice, containing properties name , capital, language, population and neighbors

1. Increase the country population by two million using dot notation.
2. Decrease the country population by one million using bracket notation.
3. Make language value in Uppercase.

4.3: Guess the Output and explain Why?

let car = {
  color: 'Blue',

  model: 2021,

  company: 'Toyota',
};

let carColor = 'Blue';

console.log(car[carColor]);

console.log(car.carColor);

4.4: Create a method describeCar inside car object in which you have to print like this in console using template literals

Company of my car is __. Its color is __. And Model of my car is __ **

4.5: Generate random numbers between 0 and 10 using trunc method of MATH object

Example

getRandomNumbers(){



}

Ouput  value  0-10

4.6: Guess the Output and Explain Why?

let  arr  = [1,2,3,4];

arr.forEach(elem  =>{

if(elem  ==  1){

continue;

}
console.log(elem);

})

4.7: Guess the Output And explain Why?

Important Note: if there is any error, How we can solve that error?

let airplane = {
  flightName: 'fly india',

  atacode: 'FI',

  ratings: 4.9,

  book(passenger, flightNum) {
    console.log(
      `${passenger} Booked flight in ${this.flightName} with flight Number ${this.atacode}${flightNum}`
    );
  },
};

let bookMethod = airplane.book;

bookMethod('john', 8754);

4.8: Guess the Output And Explain Why?

let arr = [1, 2, 3, 4];

for (let elem in arr) {
  console.log(elem);
}

4.9: You have to create a Shopping_Cart array with following features :

• addItem(itemName) : this function should add string itemName to cart

• removeItem(itemName): this function should remove any item which matches itemName. Hint : search for index of itemName and then remove it

• cartSize() : returns size of cart in terms of number of cart Items.

WOW Set 5:

Assignments

5.1: Explain difference between innerText and innerHTML in the following example?

HTML

<div id="content">
  <h2>Hello Coders</h2>
</div>

JavaScript

let content = document.getElementById('content');

console.log(content.innerHTML);

console.log(content.innerText);

## WOW Set 6:

Assignments

6.1: Create regex for password with the following validations.

1. Length of password at least of 8 characters

2. contain at least one special character

3. contain at least one alphabet (a-z) character

HTML

<form action="" class="testForm">
  <input
    type="password"
    name=""
    class="inputPass"
    placeholder="Enter Password"
  />

  <input type="submit" value="Check Password" />
</form>

JavaScript

let form = document.querySelector('.testForm');

let inputPassword = document.querySelector('.inputPass');

let requiredPasswordPattern = 'create your regex here';

form.addEventListener('submit', (e) => {
  e.preventDefault();

  let password = inputPassword.value;

  let result = requiredPasswordPattern.test(password);

  if (result == true) {
    console.log('Your password validated successfully');
  } else {
    console.log('try again with new password');
  }
});

## WOW Set 7:

Assignments

7.1: You have given array of strings. Your task is to obtain last two elements of given array using slice method?

Input;

let admins = ['john', 'paul', 'Neha', 'harry'];

Ouput[('Neha', 'harry')];

7.2: You have given an array of 5 elements(1-5). Your task is defined as below.

const arr = [1, 4, 7, 6, 8];

1. You have to delete 2 elements starting from index 2.

2. You have to add 3 new elements on index 1 choice.

3. Display the 2 deleted elements in console (from step 1)

7.3: What happens if we use negative number inside slice method?

const arr = [1, 4, 7, 6, 8];

Example : arr.slice(-2);

7.4: Write three different methods/approaches to get last element of the array?

const arr = [1, 4, 7, 6, 8];

7.5: You have given an array of nums. Create new Array with the help of nums array. In new Array each element will be a result of multiplication by 2 of the original array element

const arr = [1, 4, 7, 6, 8];

Example: Input;

let nums = [1, 2, 3, 4, 5];

output;

updatedNums = [2, 4, 6, 8, 10];

7.6 You have given an array of scores in which score of each student stored. Create a new array with the help of original scores array in which only those scores exist greater than 75%

const arr = [10, 40, 70, 60, 80];

let totalScore = 150;

let scores = [55, 76, 35, 77, 88, 97, 120, 136, 140];

7.7: You have given an array of numbers nums. You have to find sum of all array elements using reduce method?

let nums = [2, 3, 5, 7, 8, 4, 9];

7.8: You have given an array of numbers nums. You have to find the index of value 8 using built-in method of array?

let nums = [2, 3, 5, 6, 8, 6, 4, 8];

7.9: You have given an array of objects of users as below. Find the specified user with name = "John"

Also find the position (index+1) of that user inside the array?

let users = [
  {
    name: 'Paul',

    age: 24,

    verified: true,
  },

  {
    name: 'John',

    age: 21,

    verified: false,
  },

  {
    name: 'Neha',

    age: 19,

    verify: true,
  },
];

7.10: Guess the Output and explain Why?

let nums = [1, 2, 4, 5, [6, [8]], [9, 0]];

let res1 = nums.flat(1);

let res2 = nums.flatMap((elem) => elem);

console.log(res1, res2);

7.11: You have given an array of nums. Write a program to sort the elements of array in descending order using built-in method of array.

Input;

let nums = [5, 1, 4, 6, 8, 3, 9];

Output[(9, 8, 6, 5, 4, 3, 1)];

7.12: Guess the Output and Explain Why?

let arr = [1, 2, 3, 4];

let result = arr.splice(1, 2).pop();

console.log(result);

7.13: You have given an array of numbers nums You have to check if all elements of the array > 15 using built-in array method. return true or false

let nums = [16, 17, 18, 28, 22];

## WOW Set 8:

Question 1: Guess the Output And explain Why?

let strArray = [1, 2, 3, 4, 5];

let result = strArray.reverse();

console.log(result == strArray);

Question 2: You have given two arrays below as an example. Your task is to combine them into one By using array method

input;

let arr1 = [1, 2, 3, 4, 5];

let arr2 = [6, 7, 8, 9, 10];

ouput[(6, 7, 8, 9, 10, 1, 2, 3, 4, 5)];

Question 3: You have given an array of letters below. Convert that array into string of letters Without Space

input;

let arr = ['w', 'o', 'w', 'p', 'r', 'o', 'g', 'r','a','m','m','e','r','s'];

output;

('wowprogrammers');

Question 4: Guess the Output and explain why?

let arr = [11, 62, 1, 27, 8, 5];

let sorted = arr.sort();

console.log(sorted);

Question 5: Create a function 'calcAverageHumanAge', which accepts an arrays of dog's ages ('ages'), and does the following thing in order:

1. Calculate the dog age in human years using the following formula: if the dogAge <= 2 years old, humanAge = 2 \* dogAge. If the dog is > 2 years old, humanAge = 16 + dogAge

Test  data

let  arr  = [12,2,5,12,8,13,9];

Question 6: Guess the Output and Explain Why?

let arr = [1, 2, 3, 4, 5, 6, 7, 8];

let elem = arr.at(-1);

console.log(elem);

Question 7: Guess the Output and Explain why?

let arr = [1, 2, 3, 4, 5, 6, 7, 8];

let result = arr.slice(2, 5).splice(0, 2, 21).pop();

console.log(result, arr);

WOW Set 9:

Assignments

9.1: How can we get current time in millisecond of current time?

9.2: Guess the Output and Explain Why?

let currentDate = new Date();

let result1 = currentDate.getDay();

let result2 = currentDate.getDate();

console.log(result1, result2);

WOW Set 10:

Assignments

10.1: Create two variables myHobby , age . Now set their value in local storage (according to your hobby and age).

After setting also get value from local storage and display their values in console.

WOW Set 11:

Assignments

11.1: Your tasks:

1. Use a constructor function to implement a Bike. A bike has a make and a speed property. The speed property is the current speed of the bike in km/h

2. Implement an accelerate method that will increase the bike's speed by 50, and log the new speed to the console

3. Implement a brake method that will decrease the bike's speed by 25, and log the new speed to the console

4. Create 2 'Bike' objects and experiment with calling accelerate and brake multiple times on each of them

Sample Data

Data car 1: bike1 going at 120 km/h

Data car 2: bike going at 95 km/h

11.2: Re-create Question 1 But this time using ES6

class.

11.3: Guess the Output And Explain Why?

function Person(name) {
  this.name = name;
}

let me = new Person('John');

console.log(me.__proto__ == Person.prototype);

console.log(me.__proto__.__proto__ == Object.prototype);

11.4: Create constructor function inside Car class with three properties color , model , company

class Car {}

11.5: Identify all mistakes in the following class

class  Car = {

constructor(){



},

engineMethod  =  function(){

console.log("This is engine method of Car class");

}

}

11.6: Guess the Output and explain Why? And if there is any error How we can remove that error?

function Person(name, age) {
  this.name = name;

  this.age = age;

  this.brainMethod = function () {
    console.log('This is brain method of Person');
  };
}

Person.heartMethod = function () {
  console.log('This is heart method of Person');
};

let me = new Person('john', 34);

me.brainMethod();

me.heartMethod();

11.7: Create a new class Dog (which will be child class) inherited from Animal class. In Addition in Dog class add some additional properties like breedType

11.8: Guess the Output And Explain Why?

class Car {
  constructor() {}
}

let car = new Car();

console.log(Car.prototype.isPrototypeOf(Car));

console.log(Car.prototype.isPrototypeOf(car));

WOW Set 12: (OOP)

Question 1: Guess the Output and Explain Why?

function carObject(name, model) {
  let car = Object.create(constructorObject);

  car.name = name;

  car.model = model;

  this.engineMethod = function () {
    console.log('This is engine method of car');
  };

  return car;
}

let constructorObject = {
  speak: function () {
    return 'This is my car';
  },
};

let myCar = carObject('Audi', 2023);

console.log(myCar.__proto__);

Question 2: You have given an example of OOP Code. Your task is to explain the use of super keyword in Dog class.

And you have to change the code again after removing super keyword from the Dog class (You have remove those lines/statements which are not necessary after removing super keyword)

class Animals {
  constructor(name, age) {
    this.name = name;

    this.age = age;
  }

  sing() {
    return `${this.name} can sing`;
  }

  dance() {
    return `${this.name} can dance`;
  }
}

class Dogs extends Animals {
  constructor(name, age, whiskerColor) {
    super(name, age);

    this.whiskerColor = whiskerColor;
  }

  whiskers() {
    return `I have ${this.whiskerColor} whiskers`;
  }
}

let newDog = new Dogs('Clara', 33, 'indigo');

console.log(newDog);

Question 3: What are the advantages of using getter and setter method in OOP?

Question 4: You have OOP code below. And there is single error in this code? Your task is to remove that error.

Important Note: To solve this error You need to know about method chaining concept.

class Car {
  constructor(id) {
    this.id = id;
  }

  setMake(make) {
    this.make = make;
  }

  setModel(model) {
    this.model = model;
  }

  setFuelType(fuelType) {
    this.fuelType = fuelType;
  }

  getCarInfo() {
    return {
      id: this.id,

      make: this.make,

      model: this.model,

      fuelType: this.fuelType,
    };
  }
}

console.log(
  new Car(233)

    .setMake('Honda')

    .setModel('Civic')

    .setFuelType('Petrol')

    .getCarInfo()
);

Question 5: What is difference between ** proto** and prototype property of Object? Try with Example?

Question 6: create class of Person with properties name, age.

Your main task is to add static method in that class of your choice ( e.g brainMethod)

class Person {
  constructor(name, age) {
    this.name = name;

    this.age = age;
  }
}

let me = new Person('abhishek', 25);

console.log(me);

WOW Set 13( Async Js )

Assignments

13.1: Guess the Output And Explain Why?

Html Code

<!DOCTYPE  html>

<html  lang="en">

<head>

<meta  charset="UTF-8">

<meta  http-equiv="X-UA-Compatible"  content="IE=edge">

<meta  name="viewport"  content="width=device-width, initial-scale=1.0">

<title>JavaScript-CoderDost</title>

<style>

</head>

<body>

<div id="content">



<h2 id = "heading" ></h2>



</div>

<script defer src = "./script.js"></script>

</script>

</body>

</html>

JS Code

async function greeting() {
  let myPromise = new Promise(function (resolve) {
    setTimeout(function () {
      resolve('I love Programming !!');
    }, 2000);
  });

  document.getElementById('heading').innerHTML = await myPromise;
}

greeting();

13.2: Find the Logical Error in below code. And How can we solve them with callback function approach?

const movies = [{ title: `Movie 1` }, { title: `Movie 2` }];

function getMovies() {
  setTimeout(() => {
    movies.forEach((movie, index) => {
      console.log(movie.title);
    });
  }, 1000);
}

function createMovies(movie) {
  setTimeout(() => {
    movies.push(movie);
  }, 2000);
}

getMovies();

createMovies({ title: `Movie 3` });

13.3: What are the three possible State of any promise?

13.4: Solve Question 2 again But this time with the help of promise

13.5: Now re-factor Question 2 with the help of async-await keyword?

13.6: Status code starting with 404 represent which type of message/error?

WOW Set 14: (ES6)

Assignments

14.1: Guess the Output and Explain Why?

let arr = [3, 4, 5, 7, 98, 0];

let [a, b, , c] = arr;

console.log(a, b, c);

14.2: Guess the Output And Explain Why?

let arr = [1, 3, [2, 55], [9, 8, 7]];

let [a, , [b, c], d] = arr;

console.log(a, b, c, d);

14.3: Guess the Output and explain Why?

let obj = {
  name: 'John',

  age: 25,

  weight: 70,
};

let { name: objName, age } = obj;

console.log(name, age);

14.4: You have given an array of nums.Create shallow copy of that array and store them in another variable

let  nums  = [5,7,4,9,2,8];



let  newNums  =  "store Shallow copy of nums inside newNums variable")

14.5: You have given an array as below . Create a function which accept multiple elements as an argument and return last 4 element of the array

Example:

let  nums  = [1,2,3,4,5,6,7,8];

input data: 1,2,3,4,5,6,7,8

output data: 5,6,7,8

14.6: Guess the Output And Explain Why?

let nums = 0;

let result = nums ?? 50;

console.log(result);

14.7: You have given an object as below. You have to check wheather physics is the subject of that student or not, if true find the score of physics subject using optional chaining

let student = {
  Math: {
    score: 75,
  },

  physics: {
    score: 85,
  },
};

14.8: Guess the Output And Explain Why?

let nums = [2, 3, 4, 5, 6];

for (let key of nums) {
  console.log(key);
}

WOW Set 15:

Question 1: Guess the Output and Explain Why?

let arr = [1, 2, 3, 4, 5];

let arr1 = [...arr];

arr1[2] = 10;

console.log(arr, arr1);

Question 2: You have given a list of variable names written in underscore. You have to write a program to convert them into camel casing format

List  of  variable  names



Input

user_name

last_name

date_of_birth

user_password



Output

userName

lastName

dateOfBirth

userPassword

Question 3: Guess the Output and Explain why?

function fun(a, b, ...c) {
  console.log(`${a}  ${b}`);

  console.log(c);

  console.log(c[0]);

  console.log(c.length);

  console.log(c.indexOf('google'));
}

fun('apple', 'sumsung', 'amazon', 'google', 'facebook');

Question 4: Guess the Output and Explain Why?

const fruits = { apple: 8, orange: 7, pear: 5 };

const entries = Object.entries(fruits);

for (const [fruit, count] of entries) {
  console.log(`There are ${count}  ${fruit}s`);
}

Question 5: Write a program in which you have to set Default value in case of false input value using Logical Assignment Operator?

Question 6: Guess the Output and Explain Why?

let arr = new Set([1, 2, 3, 1, 2, 1, 3, 4, 6, 7, 5]);

let length = arr.size;

console.log(arr, length);

Question 7: You have given Set below. Your task is to convert that Set into an array?

input;

let set = new Set[(1, 2, 3, 2, 1, 3, 4, 12, 2)]();

output;

let arr = 'Do something here to convert....';

Question 8: Guess the Output and Explain Why?

Note : Change values of variable to examine the result.

let number = 40;

let age = 18;

let result = number > 50 ? (age > 19 ? 'pass' : 'ageIssue') : 'numberIssue';

console.log(result);

WOW Set 16: (Modern Tooling)

Assignments

16.1: You have given scenario. You are in script.js And in same directory there is another file products.js. In products.js there are two methods called createProduct and deleteProduct

• write an import and export statement properly in order to import these two methods from products.js file into the script.js

16.2 Now export only one method createProduct using default export statement?

16.3: In import statement how can we customize/change the name of function we are importing?

Example : function is defined as Addition. We want to import as 'Add'

How can can we do this?