Practice here the most popular Javascript Interview Questions and Answers for freshers.
What is JavaScript?
JavaScript is a scripting language used for creating dynamic web content and adding interactive functionality to websites.
What is the difference between JavaScript and Java?
JavaScript and Java are completely different programming languages. Java is a statically typed language used for creating standalone applications, while JavaScript is a dynamically typed language used for creating interactive web applications.
What are the basic data types in JavaScript?
The basic data types in JavaScript are Number, String, Boolean, Null, Undefined, Object, and Symbol (added in ES6).
What is a variable in JavaScript?
A variable is a container used for storing data in JavaScript. It can hold different data types and can be changed during the execution of a program.
What is the difference between let and var in JavaScript?
The main difference between let and var in JavaScript is that let has block scope, which means it is only accessible within the block of code in which it is defined, while var has function scope, which means it is accessible throughout the entire function in which it is defined.
What is the purpose of the 'use strict' directive in JavaScript?
The 'use strict' directive enables strict mode in JavaScript, which enforces stricter rules for code syntax and prevents certain types of common coding mistakes.
What is an object in JavaScript?
An object in JavaScript is a collection of key-value pairs, where the keys are strings and the values can be any data type.
What is the difference between == and === in JavaScript?
The == operator compares values for equality, while the === operator compares both values and types for equality.
What is a callback function in JavaScript?
A callback function is a function that is passed as an argument to another function and is executed when that function has completed.
What is the difference between null and undefined in JavaScript?
Null is a value that represents nothing, while undefined is a value that represents the absence of a value.
What is hoisting in JavaScript?
Hoisting is a behavior in JavaScript where variables and function declarations are moved to the top of their respective scopes during the compilation phase.
What is an event in JavaScript?
An event in JavaScript is a user or system action that triggers a response in the code.
What is a closure in JavaScript?
A closure in JavaScript is a function that has access to variables in its outer (enclosing) function's scope.
What is the purpose of the 'this' keyword in JavaScript?
The 'this' keyword refers to the object that the function is a method of, or the global object if the function is not a method of any object.
What is the difference between synchronous and asynchronous programming in JavaScript?
Synchronous programming executes code in a sequential order, while asynchronous programming allows multiple pieces of code to run concurrently.
What is a promise in JavaScript?
A promise in JavaScript is an object that represents the eventual completion or failure of an asynchronous operation.
What is the purpose of the try...catch statement in JavaScript?
The try...catch statement is used to handle errors in JavaScript code. The try block contains the code to be executed, while the catch block contains the code to handle any errors that may occur.
What is a generator function in JavaScript?
A generator function is a special type of function in JavaScript that can pause and resume its execution at certain points.
What is the purpose of the 'yield' keyword in JavaScript?
The 'yield' keyword is used inside a generator function to pause its execution and return a value to the caller.
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