Javascript Classes MCQ - Quiz

The instanceof operator is a JavaScript operator that is used to check if an object is an instance of a particular class or constructor function. It returns a boolean value indicating whether the object is an instance of the class or not.
The instanceof operator is written with the syntax object instanceof Class, where object is the object to be checked and Class is the constructor function or class to check against.
For example:
function A() {
// Properties and methods of class A
}

function B() {
// Properties and methods of class B
}

const a = new A();
console.log(a instanceof A); // Output: true
console.log(a instanceof B); // Output: false

const b = new B();
console.log(b instanceof A); // Output: false
console.log(b instanceof B); // Output: true

Here, we define two classes, A and B, and create two objects, a and b, using the new keyword. The instanceof operator is used to check if the objects are instances of the respective classes.
The first object, a, is an instance of A but not B, so the first two instanceof checks return true and false, respectively. The second object, b, is an instance of B but not A, so the last two instanceof checks return false and true, respectively.
The instanceof operator is useful for determining the type of an object at runtime and for implementing type checking in JavaScript programs.

The Object.defineProperties() method is a predefined function in the object library of JavaScript that is used to define new properties or modify existing properties on an object. It returns the object.
The Object.defineProperties() method takes an object as its first argument and a property descriptor object as its second argument. The property descriptor object can specify the characteristics of one or more properties to be added to or modified on the object.

The Object.seal() method in JavaScript is used to seal an object, which means that it prevents new properties from being added to the object and marks all existing properties as non-configurable. Sealed objects cannot be deleted, and their existing properties cannot be changed or removed.

To seal an object, you pass the object as an argument to the Object.seal() method and it returns the sealed object.

In JavaScript, there are three different objects involved in the definition of a class: the constructor object, the prototype object, and the instance object. These objects have properties that act like different kinds of class members.

The constructor object is the function that is used to create an instance of the class. It has properties that act like instance fields and instance methods.

The prototype object is an object that is shared by all instances of the class and has properties that act like class fields and class methods.

The instance object is an object that represents a single instance of the class and has properties that act like instance fields and instance methods.

A regular expression is a pattern of characters that is used to match character combinations in strings. In JavaScript, regular expressions are represented using the RegExp class. The RegExp class provides methods for working with regular expressions, such as test(), exec(), and match().

Both strings and the RegExp class have methods that use regular expressions. For example, the String.prototype.match() method returns an array of strings that match a given regular expression, and the String.prototype.replace() method replaces substrings that match a given regular expression with a replacement string.

Regular expressions are a powerful tool for pattern matching and string manipulation in JavaScript. They are often used to validate user input, search and replace text, and extract data from strings.

An object is created by calling a function and passing it some arguments. The function uses the this keyword to set the values of the object's properties based on the arguments that were passed.

The emp function is defined as a constructor function that takes two arguments: name and salary.
The name and salary properties of the object are set using the this keyword.
The changeSalary method is defined and assigned to the changeSalary property of the object using the this keyword. The changeSalary method takes a single argument: otherSalary.
An object is created using the emp constructor function and passing it the arguments "Rahul" and 30000. 
This creates an object with the name property set to "Rahul" and the salary property set to 30000.
The changeSalary method is called on the object, passing it the argument 45000. This sets the salary property of the object to 45000.
The name and salary properties of the object are written to the document using the document.write() method. The output is e.name+ 45000.


The changeSalary method uses the this keyword to refer to the current object and sets the salary property of the object to the value of the otherSalary argument. 
This allows you to change the salary of the object by calling the changeSalary method and passing it a new salary value

The Object.entries() method is a built-in method in JavaScript that returns an array of a given object's own enumerable property [key, value] pairs. The order of the properties in the array is the same as the order in which they are enumerated in a for...in loop over the object.

Modules are generally designed to run in an unmodified (or almost unmodified) environment, and should minimize the number of global symbols they define, with the goal of having no module define more than one.

"A namespace is a container that holds a set of identifiers, functions, methods, and other elements and helps to organize and distinguish them.
Modules that have multiple items in their API may return a namespace object