The mechanism that allows you to use the structure of a class and alter it for use in another class is known as "Inheritance." Inheritance in JavaScript is achieved through the prototype chain, where a child class can inherit properties and methods from a parent class, allowing for code reuse and extension.

The keyword "new" in JavaScript is used to instantiate an object from a class constructor. When you use "new" followed by a class constructor, it creates a new instance of that class, allowing you to work with objects that have the properties and methods defined in the class. It doesn't create a class, declare a variable, or define a function.

An async function can contain an await expression that pauses the execution of the async function and waits for the passed Promise to resolve or reject. This allows for more readable and sequential asynchronous code, making it easier to work with asynchronous operations.

JavaScript performs type coercion when comparing values. In this case, the empty array [] is truthy, and ![] evaluates to false. When comparing, the empty array is coerced to false, resulting in true. This behavior can be surprising and is a common gotcha in JavaScript.

JavaScript was introduced to the world in 1995. It was first released as part of Netscape Navigator 2.0. This event marked the beginning of JavaScript's journey as a popular and widely used scripting language for web development.

The comparison operator == (Equality) performs type coercion if the operands are of different types. This means JavaScript will attempt to convert the operands to the same type before making the comparison. In contrast, === (Strict Equality) checks both value and type without coercion.

A JavaScript callback function is a function that is passed as an argument to another function and is executed later, often after the completion of an asynchronous operation. It's a fundamental concept for handling asynchronous tasks and allows for flexible and event-driven programming.

The most effective way to prevent user-generated content from executing JavaScript and potentially harmful code is to implement input validation and sanitization. By validating and sanitizing user inputs, you can strip or escape any potentially malicious code, making the content safe for display. Disabling JavaScript altogether may impact the functionality of your web application.

The pop() method in JavaScript removes the last element from an array and returns the removed element. If the array is empty, pop() returns undefined. It is commonly used to remove and retrieve the last element in a stack-like fashion from the end of an array.

Adding the async keyword before a function declaration in JavaScript signifies that the function is asynchronous. This means it can use the await keyword inside to pause execution until asynchronous operations within the function are complete, improving code readability and maintainability.