Javascript Developer Interview Questions and Answers for Freshers

Callback hell refers to the situation where multiple nested callbacks make the code difficult to read and maintain.

• Occurs when multiple asynchronous operations are nested within each other

• Can lead to deeply nested code structure which is hard to follow

• Can be avoided by using promises or async/await

The '==' operator checks for equality after type coercion, while '===' checks for equality without type coercion.

• The '==' operator compares two values after converting them to a common type.

• The '===' operator compares two values without type conversion, so they must be of the same type to be considered equal.

• Example: 1 == '1' will return true because the values are equal after type coercion, but 1 === '1' will return false because they are of different types.

Promises are used for asynchronous programming in JavaScript. var is function-scoped, let is block-scoped, and const is block-scoped and cannot be reassigned.

• Promises are used to handle asynchronous operations in JavaScript.

• var is function-scoped, let is block-scoped, and const is block-scoped and cannot be reassigned.

• Example: var x = 10; let y = 20; const z = 30;

Types of loops in JavaScript include for, while, and do-while loops.

• For loop: Executes a block of code a specified number of times.

• While loop: Executes a block of code while a specified condition is true.

• Do-while loop: Executes a block of code once, and then repeats the loop as long as a specified condition is true.