What does the new operator do in js

The new operator in js does: 1. Create an empty object, and this new object will become an instance of the function; 2. Link the prototype of the new object to the prototype object of the constructor, so that the new object can Access the properties and methods defined in the constructor prototype object; 3. Assign the scope of the constructor to the new object, so that the new object can reference the properties and methods in the constructor through the this keyword; 4. Execute the constructor The code in the constructor will be used to initialize the properties and methods of the new object; 5. If there is no return in the constructor, etc.

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

In JavaScript, the new operator is used to create a new object instance. When a function is called using the new operator, it will perform the following steps:

1. Create an empty object. This new object will become an instance of the function.

2. Link the prototype of the new object to the prototype object of the constructor. This way the new object can access the properties and methods defined in the constructor prototype object.

3. Assign the scope of the constructor to the new object. In this way, the new object can refer to the properties and methods in the constructor through the this keyword.

4. Execute the code in the constructor. The code in the constructor will be used to initialize the properties of the new object.

5. If no other object is returned in the constructor, the new operator will return the newly created object instance. Otherwise, the object returned in the constructor is returned.

The following is an example that demonstrates the use of the new operator:

// 定义一个构造函数
function Person(name, age) {
  this.name = name;
  this.age = age;
}
// 使用new操作符创建一个Person对象实例
var person1 = new Person("John", 25);
// person1现在是一个Person对象实例
console.log(person1.name); // 输出: "John"
console.log(person1.age); // 输出: 25

In the above example, a new Person object instance is created by calling the Person constructor through the new operator. The name property of this new object instance is set to "John" and the age property is set to 25.

It should be noted that the new operator is actually a syntax sugar that hides some underlying details. In fact, the new operator just calls the constructor and links the constructor's prototype object to the new object's prototype chain. Therefore, we can also simulate the behavior of the new operator by performing these steps manually.

To summarize, the new operator does the following things in JavaScript: creates a new object, links the prototype chain, sets the scope, executes the constructor code, and returns a new object instance. These steps allow us to use the constructor to create an object instance and initialize the new object in the constructor.

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