What is the role of js prototype and prototype chain

The function of js prototype and prototype chain is to realize the inheritance of objects, save memory space, and improve the performance and maintainability of the code. Detailed introduction: 1. Implement the inheritance of objects. The prototype and prototype chain allow you to create an object and inherit the properties and methods of another object. When you create a new object, you can point its prototype to another object, so that the new object The object can access the properties and methods on the prototype object; 2. Save memory and improve performance. In JavaScript, each object has a prototype. Through the prototype chain, objects can share prototypes, etc.

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

Prototypes and prototype chains play an important role in JavaScript. They help us realize object inheritance, save memory and improve performance.

1. Implement object inheritance:

Prototype and prototype chain allow us to create an object and make it inherit the properties and methods of another object. When we create a new object, we can point its prototype to another object so that the new object can access the properties and methods on the prototype object. This inheritance method is called prototypal inheritance, which is an object-based inheritance method in JavaScript. Through the prototype chain, objects can look up properties and methods along the prototype chain, achieving the effect of inheritance.

Sample code:

   function Animal(name) {
     this.name = name;
   }
   Animal.prototype.sayHello = function() {
     console.log("Hello, I'm " + this.name);
   };
   function Dog(name, breed) {
     Animal.call(this, name);
     this.breed = breed;
   }
   Dog.prototype = Object.create(Animal.prototype);
   Dog.prototype.constructor = Dog;
   Dog.prototype.bark = function() {
     console.log("Woof!");
   };
   var dog = new Dog("Fido", "Labrador");
   dog.sayHello(); // 输出："Hello, I'm Fido"
   dog.bark(); // 输出："Woof!"

In this example, we define an Animal constructor, which has a sayHello method. Then we point the prototype of the Dog constructor to the prototype of the Animal constructor through the prototype chain, so that the Dog object can inherit the properties and methods of Animal. Through the prototype chain, we can easily implement object inheritance.

2. Save memory and improve performance:

In JavaScript, each object has a prototype. Through the prototype chain, objects can share properties and methods on the prototype. This means that we can define properties and methods once on the prototype object, and then all objects inheriting through the prototype can access them, without having to define them once in each object. This saves memory space and reduces repetitive code writing.

Sample code:

   function Person(name) {
     this.name = name;
   }
   Person.prototype.sayHello = function() {
     console.log("Hello, I'm " + this.name);
   };
   var person1 = new Person("Alice");
   var person2 = new Person("Bob");
   person1.sayHello(); // 输出："Hello, I'm Alice"
   person2.sayHello(); // 输出："Hello, I'm Bob"

In this example, we define a sayHello method through prototype, and then we create two Person objects. These two objects share the sayHello method on the prototype. They do not need to define the sayHello method in their own objects, thus saving memory space. If we define the sayHello method in each object, each object will occupy additional memory space.

In addition, since all objects share properties and methods on the prototype chain, when we modify properties and methods on the prototype, all objects inherited through the prototype chain will be affected. This improves performance and code maintainability because we only need to modify the properties and methods on the prototype once, rather than modifying each object one by one.

Summary:

Prototypes and prototype chains play an important role in JavaScript. They help us realize object inheritance, save memory space, and improve the performance and maintainability of code. Through prototypes and prototype chains, we can flexibly organize and manage the relationships between objects and achieve code reuse and expansion. Prototype and prototype chain are essential concepts for understanding JavaScript's object-oriented programming and inheritance mechanisms.

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