What does new operator do in js

What the new operator does in JS requires specific code examples

In JavaScript, the new operator is used to create object instances. Its main function is to create a new object by calling the constructor and point the prototype of the new object to the prototype property of the constructor. This process involves the following steps:

1. Create a new object

When using new to call a function, JavaScript will create a new empty object in memory as an instance of this function.

2. Point the prototype of the new object to the prototype property of the constructor

By assigning the prototype property of the constructor to the prototype property of the new object, you can ensure that the new object can Access all properties and methods defined in the constructor. In this way, the new object can inherit the corresponding properties and methods from the constructor's prototype chain.

3. Assign the scope of the constructor to the new object (that is, point this to the new object)

When the constructor is called, the this keyword in the function points to the new object object so that the constructor can add properties and methods on the new object.

4. Execute the code in the constructor

The constructor can receive parameters and can initialize the new object or set its initial property values ​​in code.

5. Return a new object

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

The following is a specific code example to illustrate the use of the new operator:

// 定义一个构造函数
function Person(name, age) {
  this.name = name;
  this.age = age;
}

// 在构造函数的原型上添加一个方法
Person.prototype.sayHello = function() {
  console.log("Hello, my name is " + this.name + ", I am " + this.age + " years old.");
}

// 使用new操作符创建一个新的Person对象
var person1 = new Person("Alice", 25);

// 调用Person对象的sayHello方法
person1.sayHello(); // 输出: Hello, my name is Alice, I am 25 years old.

In this example, we define a Person constructor and then create a new one through the new operator Person object instance person1. This new object instance has the name and age properties defined through the constructor, and can call the sayHello method on the prototype.

To summarize, the new operator is used in JavaScript to create object instances and ensure that the new object can access the properties and methods defined in the constructor. It is a very common concept in object-oriented programming and is often used in actual development.

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