Q1 What is the purpose of JavaScript in web development?

Q2 Which keyword is used for declaring a variable in JavaScript that can be reassigned?

Q3 In JavaScript, which of the following is a valid variable name?

Q4 Which data type in JavaScript is used to represent logical values?

Q5 What does the undefined value in JavaScript represent?

Q6 What will be the output of the following code?
console.log(typeof null);

Q7 What is the output of the following code snippet?
var a = 10;
console.log(a);

Q8 Which statement is used to execute a block of code multiple times in JavaScript?

Q9 What does the if statement in JavaScript do?

Q10 Which of the following is not a loop structure in JavaScript?

Q11 In a switch statement, what keyword is used to terminate a case in JavaScript?

Q12 What will be the output of the following code?
let a = 2;
if(a > 3) {
console.log('Yes');
} else {
console.log('No');
}

Q13 In a for loop, what are the three optional expressions, separated by semicolons?

Q14 Identify the problem in this code:
let i = 0;
while (i < 3) {
console.log(i);
}

Q15 What is the result of trying to extend the length of an array using a function in JavaScript?
function extendArray(arr) {
arr.push(5);
}
let myArr = [1, 2, 3];
extendArray(myArr);
console.log(myArr.length);

Q16 What does the following function return?
function checkEven(number) {
return number % 2 === 0;
}
console.log(checkEven(3));

Q17 In JavaScript, how can you check if a variable is an array?

Q18 What is the output of the following code?
let fruits = ['apple', 'banana', 'mango'];
console.log(fruits[1]);

Q19 Consider the following code:
let arr = [1, 2, 3];
arr[5] = 5;
console.log(arr.filter(x => x === undefined).length);
What is the output?

Q20 Spot the mistake in this code snippet:
let data = [1, 2, 3];
delete data[1];
console.log(data[1]);

Q21 What will be the output of console.log(typeof {})?

Q22 In JavaScript, what is a method?

Q23 How do you create a new object in JavaScript?

Q24 What is the purpose of the this keyword in JavaScript objects?

Q25 What is the result of accessing a property that doesn’t exist on an object?

Q26 What is the output of the following code snippet?
let obj = { a: 1, b: 2 };
console.log(obj.a);

Q27 Consider the code:
let person = { name: 'Alice', age: 25 };
delete person.age; console.log(person.age);
What is the output?

Q28 Given the following code, what is printed to the console?
let obj1 = { a: 1 };
let obj2 = { a: 1 };
console.log(obj1 === obj2);

Q29 What does DOM stand for in web development?

Q30 How can you change the text content of an HTML element in the DOM using JavaScript?