JavaScript Core Concepts

What are the different data types in JavaScript?

• string, number, boolean, object, function, undefined, and symbol

• apple, banana, orange, grape

• cat, dog, bird, fish

• red, blue, green, yellow

Explain the difference between '==' and '===' operators in JavaScript.

• === checks for equality of value, while == checks for equality of value and type

• == checks for equality of value and type, while === checks for equality of value

• == and === are interchangeable and can be used interchangeably in JavaScript

• == checks for equality of value, while === checks for equality of value and type

What are the different types of control structures in JavaScript?

• try-catch statement, switch-case statement, do-until loop

• if statement, switch statement, for loop, while loop, and do-while loop

• if-else statement, repeat statement, for-each loop

• while-do statement, if-else-if statement, for-in loop

Explain the concept of function scope in JavaScript.

• Variables declared inside a function are accessible globally

• Variables declared inside a function are only accessible within that function.

• Variables declared inside a function are accessible outside of the function

• Function scope only applies to arrow functions

How do you declare and initialize an array in JavaScript?

• var arrayName = [];

• arrayName = {}

• arrayName = [1, 2, 3]

• arrayName = new Array()

What is the purpose of switch case in JavaScript?

• To execute different code blocks based on different conditions.

• To define the layout of a webpage

• To calculate mathematical operations

• To create loops in the code

What is the syntax for declaring a variable in JavaScript?

• var variableName;

• variableName = new variable();

• variableName = var;

• variableName var;

How do you access the value of a property in an object in JavaScript?

• By using dot notation or bracket notation

• By using semicolon notation

• By using comma notation

• By using arrow notation

What is the use of '&&' and '||' operators in JavaScript?

• They are used for addition and subtraction operations.

• They are used for looping through arrays.

• They are used for string concatenation.

• They are used for logical AND and logical OR operations.

Explain the concept of hoisting in JavaScript.

• Hoisting is a JavaScript mechanism where variables and function declarations are completely ignored during the compilation phase.

• Hoisting is a JavaScript mechanism where variables and function declarations are moved to the top of their containing scope during the compilation phase.

• Hoisting is a JavaScript mechanism where variables and function declarations are moved to the bottom of their containing scope during the compilation phase.

• Hoisting is a JavaScript mechanism where variables and function declarations are only moved to the top if they are explicitly marked with a special keyword.