Why are there prototypes and prototype chains?

Prototypes and prototype chains exist because objects in JavaScript are not created through classes, but through prototypes: In JavaScript, every object has a prototype object, which acts as the The template defines the default behavior of the object. Each prototype object can also have its own prototype object, forming a prototype chain.

# Operating system for this tutorial: Windows 10 system, Dell G3 computer.

JavaScript is a programming language based on prototypes. Unlike other languages, objects in JavaScript are not created through classes, but through prototypes. In JavaScript, every object has a prototype object, which acts as a template for the object and defines the object's default behavior. Each prototype object can also have its own prototype object, forming a prototype chain.

This prototype-based approach has historical roots. When JavaScript was first born, its designer Brendan Eich was influenced by Self and Smalltalk, two object-oriented programming languages. The Self language uses prototypal inheritance as the main inheritance method, while Smalltalk uses class inheritance as the main inheritance method. Since the goal of JavaScript is to create a simple and easy-to-use web scripting language, prototypal inheritance is chosen as a more flexible and concise method.

Prototypes and prototype chains play a very important role in JavaScript. They enable JavaScript to achieve inheritance and code reuse. Through prototypal inheritance, we can create new objects from existing objects, and add, modify, or delete properties and methods on the new objects to achieve code reuse and expansion. The prototype chain allows objects in JavaScript to look up properties and methods through the prototype chain, so that the inheritance of properties and methods can be realized and the writing of repeated code can be reduced.

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