The Prototype Property. Thus, it finds toString() method in the prototype object of Object function and so we can call studObj.toString(). Prototype - Object extend() Method - This method copies all properties from the source to the destination object. If JavaScript finds a prototype, it continues to search for map in that prototype. Such a registration "adds fields" to the debugger's visualization of any type which matches the signature rather than taking it over entirely. Prototypes. This works with the help of Object.setPrototypeOf() with which we are able to set the prototype of obj2 to obj1, so that super is able to find method1 on obj1. What if you wanted to modify the entire existing class to add new functionality? Now we will learn how prototypes can be used to extend objects. The class syntax does not introduce a new object-oriented inheritance model to JavaScript. Nearly all objects in JavaScript are instances of Object; a typical object inherits properties (including methods) from Object.prototype, although these properties may be shadowed (a.k.a. Fortunately, JavaScript is a very powerful object-oriented programming language. In fact, JavaScript objects also have one additional attribute: a pointer to another object. All objects in JavaScript inherit properties and methods from another object called prototype. Prototyping allows objects to inherit, override, and extend functionality provided by other objects in a similar manner as inheritance, overriding, abstraction, and related technologies do in C#, Java, and other languages. To better understand prototyping, take a look at the example below. For instance, ... [Prototype]] In JavaScript, objects have a special hidden property [[Prototype]] (as named in the specification), that is either null or references another object. The key concept here is prototype-based inheritance. If it still cannot find it there then it goes up in the heirarchy and check prototype object of Object function because all the objects are derived from Object in JavaScript, and look for toString() method. Notice that the Global and Math objects are excluded. Every object you create in JavaScript has a prototype property by default that can be accessed. You can easily extend the String object to add a method. Extending an object by adding a custom method can be quite convenient, but it only applies to that particular object's instance. This is used by Prototype to simulate inheritance by copying to prototypes. This is called Prototype chaining. If it isn’t clear enough, let me show you how much it doesn’t introduce new OO model in JS. A constructor for an object intended to be placed in the array returned from initializeScript, this represents an extension of a native type described via a type signature by a JavaScript prototype or ES6 class. We call this pointer the object's prototype. In JavaScript, there are set of built-in Objects such as Object, Array, Date, Function etc and each of those objects will have respective prototype objects attached to it. JavaScript is often described as a prototype-based language — to provide inheritance, objects can have a prototype object, which acts as a template object that it inherits methods and properties from. Object.prototype.__proto__ Points to the object which was used as prototype when the object was instantiated. The prototype object of JavaScript isn't exactly as flashy and fun to learn as say, document.bgColor or window.open, and the rewards aren't always instant. This has changed for the better. As the name suggests, prototype pollution refers to an attacker's ability to modify a JavaScript object's prototype. I think it’s OK if it is a function that actually makes sense for all Array objects (such as your example) but it can be easily abused (what can’t?) 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