A detailed explanation of JavaScript's inheritance mechanism

As a dynamic, weak-type programming language, JavaScript inheritance is an important concept in object-oriented programming. In JavaScript, inheritance allows one object to inherit properties and methods from another object. This article will introduce in detail the inheritance mechanism in JavaScript, including prototype chains, constructors, prototype objects and several methods to implement inheritance.

1. Prototype Chain

In JavaScript, each object has an internal property [[Prototype]] which points to the prototype object of the constructor used when creating the object. This prototype object itself may also have a prototype attribute, which forms a chain structure, namely a prototype chain. When we try to access an object's properties or methods, the JavaScript engine first looks on the object. If it cannot be found, it will search up along the prototype chain until the property or method is found, or it will arrive (the original ancestor of all objects).

2. Constructor

In JavaScript, a constructor is a special function that is used to initialize an object. When we usenewWhen a keyword creates an object, it is actually calling the constructor, and the internal [[Prototype]] attribute of this object will be set to the prototype attribute of the constructor.

3. Prototype Object

Each function has a prototype property, which is an object that contains properties and methods that can be inherited by all objects created by the function. When we create an object through the constructor, the internal [[Prototype]] attribute of the object will point to the prototype object of the constructor.

4. Methods to implement inheritance

4.1 Prototype chain inheritance

Protochain inheritance is the most natural way of inheritance in JavaScript. Inheritance can be achieved by pointing the prototype of one object to another.

function SuperType(name) {
   = name;
}

 = function() {
  ();
};

function SubType(name, age) {
  (this, name); // Call the constructor of the parent class   = age;
}

 = (); // Set the prototype of the subclass to an instance of the parent class = SubType; // Fix constructor pointer = function() {
  ();
};

4.2 Constructor inheritance

Constructor inheritance is to initialize objects of subclasses by borrowing the constructor of the parent class. This can be donecallandapplyMethod implementation.

function SuperType(name) {
   = name;
}

function SubType(name, age) {
  (this, name); // Call the constructor of the parent class   = age;
}

 = new SuperType(); // Create a new object through the parent class constructor and assign it to the subclass prototype = SubType; // Fix constructor pointer

4.3 Combination inheritance

Combination inheritance is a mixture of prototype chain inheritance and constructor inheritance, which tries to take the strengths of both.

function SuperType(name) {
   = name;
   = ['red', 'blue', 'green'];
}

 = function() {
  ();
};

function SubType(name, age, job) {
  (this, name); // Inheritance attributes   = age;
   = job;
}

// Borrow the constructor to inherit attributes = new SuperType(); // Inherit the properties of SuperType = SubType; // Fix constructor pointer
// Borrow prototype chain inheritance method = function() {
  ();
};

// Prototype object on the prototype chain = ['black', 'white', 'gray'];

5. Conclusion

JavaScript's inheritance mechanism provides flexible ways to implement property and method sharing between objects. By understanding prototype chains, constructors, and prototype objects, we can better create complex and maintainable code using JavaScript. In actual development, according to different needs, we can choose the most appropriate inheritance method to design our classes and objects.

The above is a detailed explanation of the JavaScript inheritance mechanism in detail in this article. For more information about the JavaScript inheritance mechanism, please pay attention to my other related articles!