JavaScript Overview and Data Types

JavaScript is a high-level, interpreted programming language primarily used for creating interactive web pages.

JavaScript supports strings, numbers, booleans, null, undefined, objects, and symbols.

Variables in JavaScript can be declared using the var, let, or const keywords.

<p><code>var</code> has function scope, <code>let</code> has block scope, and <code>const</code> is used to declare constants whose value cannot be reassigned.</p> Signup and view all the answers

<p><code>==</code> is used for loose equality comparison, whereas <code>===</code> is used for strict equality comparison.</p> Signup and view all the answers

<p>Single-line comments are denoted by <code>//</code>, and multi-line comments are enclosed between <code>/*</code> and <code>*/</code>.</p> Signup and view all the answers

<p>Primitive data types include strings, numbers, booleans, null, undefined, and symbols.</p> Signup and view all the answers

<p>The <code>typeof</code> operator is used to determine the type of a variable or an expression.</p> Signup and view all the answers

<p>Hoisting is JavaScript's default behavior of moving variable and function declarations to the top of their containing scope during compilation.</p> Signup and view all the answers

<p><code>NaN</code> stands for 'Not-a-Number' and is a value returned when a mathematical operation cannot produce a meaningful result.</p> Signup and view all the answers

<p>Closures are functions that have access to their outer function's scope, even after the outer function has finished executing.</p> Signup and view all the answers

<p>Higher-order functions are functions that operate on other functions, either by taking them as arguments or by returning them.</p> Signup and view all the answers

<p>A callback function is a function passed as an argument to another function, which is then invoked inside the outer function.</p> Signup and view all the answers

<p>Event delegation is a technique where a single event listener is attached to a parent element to listen for events that occur on its children.</p> Signup and view all the answers

<p>Prototypal inheritance is the mechanism by which objects in JavaScript inherit properties and methods from other objects, known as prototypes.</p> Signup and view all the answers

<p>The <code>this</code> keyword refers to the object on which a method is being invoked or the context in which a function is called.</p> Signup and view all the answers

<p>JavaScript uses mechanisms such as callbacks, promises, and async/await to handle asynchronous operations.</p> Signup and view all the answers

<p>Promises are objects representing the eventual completion or failure of an asynchronous operation.</p> Signup and view all the answers

<p><code>null</code> represents the intentional absence of any object value, while <code>undefined</code> represents the absence of a defined value.</p> Signup and view all the answers

<p>The event loop is a mechanism that handles asynchronous operations in JavaScript, ensuring they are executed in a non-blocking manner.</p> Signup and view all the answers

<p><code>null</code> is an explicitly assigned value, <code>undefined</code> indicates a declared variable without an assigned value, and <code>undeclared</code> refers to variables that have not been declared.</p> Signup and view all the answers

<p>Event-driven programming is a paradigm where the flow of the program is determined by events such as user actions, network requests, or timer events.</p> Signup and view all the answers

<p>Synchronous JavaScript executes code sequentially, while asynchronous JavaScript allows for operations to run concurrently, not blocking the execution.</p> Signup and view all the answers