Javascript Interview Preparation
Guide
Javascript interview preparation involves studying the fundamentals of the language such as syntax, data types, functions, and events. It also includes practicing coding exercises and solving problems to improve technical skills. Additionally, being familiar with popular Javascript frameworks, libraries, and their implementation is essential. It is also important to brush up on HTML and CSS as they are closely related to Javascript. Understanding common interview questions and being able to articulate your thought process and problem-solving skills effectively can also help in excelling in a Javascript interview.
To Download Our Brochure: https://www.justacademy.co/download-brochure-for-free
Message us for more information: +91 9987184296
1 - What is JavaScript?
JavaScript is a popular programming language used for creating interactive and dynamic web content. It is based on the concept of using small pieces of code to manipulate elements on a webpage, making it highly versatile and flexible for web development.
2) What are the different data types in JavaScript?
The data types in JavaScript are: number, string, boolean, null, undefined, object, and symbol (added in ES6). These data types are used to store different types of information and are essential for performing operations and making decisions in a program.
3) What is the difference between == and === in JavaScript?
The double equals (==) compares the values of two operands, whereas the triple equals (===) compares both the values and the data types. This means that the triple equals is more strict and will return false if the data types do not match, while the double equals will perform type coercion and return true if the values can be interpreted as equal.
4) What is a closure in JavaScript?
A closure in JavaScript is a function that has access to variables in its outer scope, even after the outer function has returned. This is because the inner function maintains a reference to the variables in its surrounding scope, creating a closure. Closures are often used for creating private variables and for creating callbacks.
5) What is hoisting in JavaScript?
Hoisting is a mechanism where variables and function declarations are moved to the top of their scope during compilation. This means that they can be used before they are declared, but their values will be set to undefined until they are assigned a value. It is important to note that only the declaration is hoisted, not the assignment of values.
6) What is the use of the “this” keyword in JavaScript?
The “this” keyword in JavaScript refers to the object that the code is currently executing in. It is often used to refer to the current object, but its value can change depending on the context in which it is used. In a global context, “this” refers to the global object, while in a function, it refers to the object that the function is a method of.
7) What is an IIFE and why is it used?
IIFE stands for Immediately Invoked Function Expression and it is a way of encapsulating code in its own scope. It is often used to avoid polluting the global namespace, as the variables and functions declared within an IIFE are not accessible from outside. It is executed immediately and the returned value can be assigned to a variable.
8) What are the different ways to create an object in JavaScript?
There are several ways to create an object in JavaScript: using the Object constructor, using object literal notation, using the create method, using a constructor function, and using ES6's class syntax. Each method has its own advantages and can be used depending on the specific use case.
9) What is a callback function in JavaScript?
A callback function in JavaScript is a function that is passed as an argument to another function and is executed once the first function has completed its task. It is commonly used in asynchronous operations, such as event handlers, to handle the response once it is available.
10) What is the difference between let and var in JavaScript?
The main difference between let and var in JavaScript is their scoping. Variables declared with var are function scoped, meaning they are accessible within the entire function, while variables declared with let are block scoped, meaning they are only accessible within the block they are declared in.
11) What is event bubbling in JavaScript?
Event bubbling is a mechanism where when an event is triggered on an element, it will also trigger on all of its parent elements. This means that the event will “bubble” up the DOM tree until it is handled or reaches the top of the DOM. Event delegation and stopping propagation can be used to control event bubbling.
12) What is a promise in JavaScript?
A promise in JavaScript is an object that represents the eventual completion or failure of an asynchronous operation. It is commonly used for handling asynchronous tasks, such as network requests, and allows for cleaner and more readable code compared to using callbacks.
13) How do you handle errors in JavaScript?
To Download Our Brochure: Click Here
Message us for more information: +91 9987184296
Errors in JavaScript can be handled using try catch blocks, which allows for code to be executed normally and catch any thrown errors. This is especially useful for handling asynchronous code and handling specific types of errors. Additionally, debugging tools and error handling libraries can also be used.
14) What is event delegation in JavaScript?
Event delegation is a technique where instead of attaching event handlers to individual elements, the event handler is attached to a parent element that contains the desired child elements. This reduces the number of event handlers and is useful for handling events on elements that are dynamically added to the DOM.
15) What is the difference between “null” and “undefined” in JavaScript?
Null and undefined are both primitive data types in JavaScript, but with different meanings. Null is a value that represents the absence of a value, while undefined means a variable has been declared but has not been assigned a value. In other words, null is a value that is intentionally assigned, while undefined is unintentionally not assigned.
Browse our course links : https://www.justacademy.co/all-courses
To Join our FREE DEMO Session: Click Here
Contact Us for more info:
- Message us on Whatsapp: +91 9987184296
- Email id: info@justacademy.co
Java 2 Years Experience Interview Questions
Javascript Interview Questions For 1 Year Experience
Django Interview Questions And Answers
