The principles and impact of prototypes and prototype chains in JavaScript development-JS Tutorial-php.cn

The principles and impact of prototypes and prototype chains in JavaScript development

王林

Release： 2024-01-10 21:29:55

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The principles and impact of prototypes and prototype chains in JavaScript development

The principles of prototype and prototype chain and their impact on JavaScript development

In JavaScript, prototype and prototype chain are the key to understanding the language Central to the concepts of objects and inheritance. Understanding the principles of prototypes and prototype chains is very important for JavaScript developers.

First, let us understand the concept of prototype. Every JavaScript object has a prototype, which is an object that contains shared properties and methods. When you create an object, you define the object's initial properties and methods by using a constructor function. The constructor uses the keyword this to refer to the newly created object, and then by defining methods and properties on the constructor's prototype, these methods and properties can be shared by all objects created by the constructor.

For example, we define a constructor named Person to create a person object:

function Person(name, age) {
  this.name = name;
  this.age = age;
}

Person.prototype.sayHello = function() {
  console.log('Hello, my name is ' + this.name);
};

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Here, we define a Person Constructor, and defines a sayHello method on the prototype of the constructor. When we create a new person object through new Person('John', 30), the object will inherit sayHello## on the prototype of the Person constructor #method.

Next, let us understand the concept of prototype chain. The prototype chain is a mechanism for looking up properties and methods through an object's prototype. When we try to access a property or method of an object, the JavaScript engine first looks for whether the object itself has the property or method. If not found, it will continue to search on the prototype of the object until the property or method is found or the prototype chain is reached. top(Object.prototype).

For example, if we create a

Student object and try to use the sayHello method:

function Student(name, age, school) {
  Person.call(this, name, age);
  this.school = school;
}

Student.prototype = Object.create(Person.prototype);
Student.prototype.constructor = Student;

var john = new Student('John', 20, 'ABC University');
john.sayHello(); // 调用继承自Person原型上的sayHello方法

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Here, we create a

Student constructor, which inherits from Person constructor. We set the prototype of the Student constructor to the prototype of the Person constructor by calling the Object.create method, so that the Student object becomes Able to access the sayHello method defined on the Person prototype.

The impact of prototypes and prototype chains on JavaScript development is huge. They provide a flexible and powerful inheritance mechanism that allows us to organize and reuse code more efficiently. By using prototypes, we can share methods and properties during object creation instead of defining them separately in each object, which saves memory and improves performance. At the same time, the prototype chain provides a mechanism to dynamically find properties and methods, making it easy to modify and extend objects.

Of course, there are also some considerations for prototypes and prototype chains. Because objects in a prototype chain share methods and properties on the prototype, you need to be careful when modifying the prototype to avoid inadvertently affecting other objects. In addition, the search of the prototype chain is a dynamic process, which may affect the performance of the code. Therefore, prototypes and prototype chains need to be used rationally during the design and development process to avoid potential problems.

To summarize, prototypes and prototype chains are the core concepts of objects and inheritance in JavaScript. By correctly understanding and using prototypes and prototype chains, we can better organize and reuse code, and be able to extend and modify objects more easily. They are an integral part of JavaScript development.

Reference code example:

function Person(name, age) {
  this.name = name;
  this.age = age;
}

Person.prototype.sayHello = function() {
  console.log('Hello, my name is ' + this.name);
};

function Student(name, age, school) {
  Person.call(this, name, age);
  this.school = school;
}

Student.prototype = Object.create(Person.prototype);
Student.prototype.constructor = Student;

var john = new Student('John', 20, 'ABC University');
john.sayHello();

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The above code defines a

Person constructor and a Student constructor. The Student constructor inherits from the Person constructor and accesses the sayHello method on the Person prototype through the prototype chain. Finally, we create a Student object and call the sayHello method.

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