JavaScript Interview Questions and Answers
Q: What is JavaScript?
A: JavaScript is a programming language that is used to create dynamic,
interactive web pages. It is a client-side scripting language that runs on the
web browser and is used to add interactivity to web pages.
Q: What is the typeof operator used for in JavaScript?
A: The typeof operator is used to determine the data type of a value or
variable in JavaScript.
Q: What is scope in JavaScript?
A: Scope refers to the area of the program where a variable or function is
accessible. In JavaScript, there are two types of scope: global scope and local
scope.
Q: What is event delegation in JavaScript?
A: Event delegation is a technique where a single event listener is attached
to a parent element, which then handles events triggered by its child
elements.
Q: What is the difference between a for loop and a forEach
loop?
A: A for loop is a traditional loop that iterates over an array or object, while a
forEach loop is a method of an array that iterates over its elements.
Q: What is a callback function?
, A: A callback function is a function that is passed as an argument to another
function and is called when the first function is finished.
Q: What is a closure in JavaScript?
A: A closure is a function that has access to variables in its outer scope, even
after the outer function has returned.
Q: What is the difference between a let and a const
declaration?
A: A let declaration allows the variable to be reassigned, while a const
declaration does not allow reassignment after it has been assigned a value.
Q: What is JSON?
A: JSON stands for JavaScript Object Notation and is a lightweight data
interchange format that is easy to read and write for humans and machines.
Q: What is a promise in JavaScript?
A: A promise is an object that represents a value that may not be available
yet, and allows you to attach callbacks to handle success or failure.
Q: What is the purpose of the keyword "this" in JavaScript?
A: The this keyword refers to the current object that the code is being
executed in. Its value depends on the context in which it is used.
What is the difference between a named function expression
and an anonymous function expression?
Q: What is JavaScript?
A: JavaScript is a programming language that is used to create dynamic,
interactive web pages. It is a client-side scripting language that runs on the
web browser and is used to add interactivity to web pages.
Q: What is the typeof operator used for in JavaScript?
A: The typeof operator is used to determine the data type of a value or
variable in JavaScript.
Q: What is scope in JavaScript?
A: Scope refers to the area of the program where a variable or function is
accessible. In JavaScript, there are two types of scope: global scope and local
scope.
Q: What is event delegation in JavaScript?
A: Event delegation is a technique where a single event listener is attached
to a parent element, which then handles events triggered by its child
elements.
Q: What is the difference between a for loop and a forEach
loop?
A: A for loop is a traditional loop that iterates over an array or object, while a
forEach loop is a method of an array that iterates over its elements.
Q: What is a callback function?
, A: A callback function is a function that is passed as an argument to another
function and is called when the first function is finished.
Q: What is a closure in JavaScript?
A: A closure is a function that has access to variables in its outer scope, even
after the outer function has returned.
Q: What is the difference between a let and a const
declaration?
A: A let declaration allows the variable to be reassigned, while a const
declaration does not allow reassignment after it has been assigned a value.
Q: What is JSON?
A: JSON stands for JavaScript Object Notation and is a lightweight data
interchange format that is easy to read and write for humans and machines.
Q: What is a promise in JavaScript?
A: A promise is an object that represents a value that may not be available
yet, and allows you to attach callbacks to handle success or failure.
Q: What is the purpose of the keyword "this" in JavaScript?
A: The this keyword refers to the current object that the code is being
executed in. Its value depends on the context in which it is used.
What is the difference between a named function expression
and an anonymous function expression?
