JavaScript is the most popular programming language in the world, and is the language of the web. It's used to build interactive websites, web applications, and mobile apps. JavaScript is a high-level, dynamic, and interpreted programming language that is supported by all modern web browsers. It's a versatile language that can be used for a wide range of applications, from simple scripts to complex web applications.
Preparing for a JavaScript interview can be challenging, as the language is constantly evolving and new features are being added all the time. This list of JavaScript interview questions and answers covers a wide range of topics, from basic syntax and data types to more advanced concepts like closures and promises. By reviewing these questions and answers, you can gain the confidence you need to ace your next JavaScript interview.
JavaScript is a high-level, interpreted programming language that conforms to the ECMAScript specification. It is widely used for client-side web development.
JavaScript has several key features that make it a popular choice for web development.
'==' is the equality operator in JavaScript, which compares two values for equality, but it does not check for the data type.
Hoisting is a JavaScript mechanism where variables and function declarations are moved to the top of their containing scope during the compilation phase.
A closure is a function that retains access to its outer scope's variables even after the outer scope has finished execution.
In JavaScript, 'null' is a value that represents the intentional absence of any object value, while 'undefined' is a value that indicates the absence of a defined value.
There are several ways to create objects in JavaScript, including object literals, constructor functions, and the 'Object.create()' method.
Event bubbling and event capturing are two mechanisms used in JavaScript to describe the order in which events are handled by nested elements.
'var', 'let', and 'const' are used to declare variables in JavaScript, but they have some key differences.
The event loop is a mechanism in JavaScript that allows asynchronous events to be handled in a non-blocking way.
A promise is an object that represents the eventual completion (or failure) of an asynchronous operation and its resulting value.
A callback is a function that is passed as an argument to another function and is executed after its parent function has completed.
'null', 'undefined', and 'NaN' are all values used to represent different types of absence or error in JavaScript.
'=>' is the arrow function syntax introduced in ES6, which provides a more concise way to write function expressions.
Scope refers to the visibility and accessibility of variables and functions in a particular part of a program.
Event delegation is a technique in JavaScript where you attach an event listener to a parent element instead of individual child elements.
There are several ways to loop through an array in JavaScript, including 'for' loops, 'forEach()', 'for...in' loops, and 'for...of' loops.
'map()' and 'forEach()' are both methods used to iterate over arrays in JavaScript, but they have some key differences.
'slice()' and 'splice()' are both methods used to manipulate arrays in JavaScript, but they have different purposes.
There are several types of errors in JavaScript, including syntax errors, runtime errors, and logical errors.
'stopPropagation()' and 'preventDefault()' are both methods used to control the behavior of events in JavaScript, but they have different purposes.
'this' refers to the current DOM element in JavaScript, while '$(this)' is a jQuery object that wraps the current DOM element.
AJAX (Asynchronous JavaScript and XML) is a technique used in web development to send and receive data from a server asynchronously.
A closure is a function that retains access to its outer scope's variables even after the outer scope has finished execution.
'==' is the equality operator in JavaScript, which compares two values for equality, but it does not check for the data type.
The 'use strict' mode is a feature in JavaScript that enables stricter parsing and error handling in your code.
'undefined' and 'null' are both values used to represent the absence of a value in JavaScript, but they are used in different contexts.