JavaScript深入之从原型到原型链 ChatGTP

JavaScript深入之从原型到原型链

Please explain the following js code

function Person() {

}
var person = new Person();
person.name = 'Kevin';
console.log(person.name) 

 

Sure! The code that you provided defines a Person function and creates a new person object using the new keyword.

Then, it sets the name property of the person object to 'Kevin'

and logs the value of the name property to the console.

Here's a step-by-step explanation of what the code is doing:

1. The Person function is defined like this:

    
2. function Person() { }

   This is a simple function that doesn't take any arguments and doesn't have a body. It is intended to be used as a constructor function, which means that it will be used to create new objects.

3. A new person object is created using the Person function and the new keyword like this:

    
4. var person = new Person();

   This creates a new object with the Person function as its constructor. The Person function doesn't have any properties or methods, so the person object will be empty.

5. The name property of the person object is set like this:

    

person.name = 'Kevin';

This adds a new name

 

What's the prototype used in following code:

function Person() {

}
Person.prototype.name = 'Kevin';
var person1 = new Person();
var person2 = new Person();
console.log(person1.name) // Kevin
console.log(person2.name) // Kevin

In the code that you provided, the prototype property of the Person function is used to add a name property to all objects created with the Person constructor function.

Here's a step-by-step explanation of what the code is doing:

1. The Person function is defined like this:

    
2. function Person() { }

   This is a simple function that doesn't take any arguments and doesn't have a body. It is intended to be used as a constructor function, which means that it will be used to create new objects.

3. The prototype property of the Person function is used to add a name property to all objects created with the Person function like this:

    
4. Person.prototype.name = 'Kevin';

   This sets the name property of the prototype object of the Person function to 'Kevin'. This means that all objects created with the Person function will have a name property with the value 'Kevin'.

5. Two new person objects are created using the Person function and the new keyword like this:

    
6. var person1 = new Person(); var person2 = new Person();

   These statements create two new objects with the Person function as their constructor. Because the Person function's prototype object has a name property with the value 'Kevin', both of these objects will have a name property with the value 'Kevin'.

7. The name property of the person1 and person2 objects is logged to the console like this:

    

4. console.log(person1.name); // Output: Kevin console.log(person2.name); // Output: Kevin

   These statements log the value of the name property of the person1 and person2 objects to the console. Because both objects were created with the Person function and have the name property defined on the prototype object of the Person function, the output will be 'Kevin' for both objects.

I hope this helps! Let me know if you have any other questions.

 

Please explain the following code of js:

function Person() {

}
var person = new Person();
console.log(person.__proto__ === Person.prototype); // true

The code that you provided compares the __proto__ property of the person object with the prototype property of the Person function.

Here's a step-by-step explanation of what the code is doing:

1. The Person function is defined like this:

    
2. function Person() { }

   This is a simple function that doesn't take any arguments and doesn't have a body. It is intended to be used as a constructor function, which means that it will be used to create new objects.

3. A new person object is created using the Person function and the new keyword like this:

    
4. var person = new Person();

   This creates a new object with the Person function as its constructor. The Person function doesn't have any properties or methods, so the person object will be empty.

5. The __proto__ property of the person object is compared to the prototype property of the Person function like this:

    

3. console.log(person.__proto__ === Person.prototype); // true

   This statement compares the __proto__ property of the person object with the prototype property of the Person function.

The __proto__ property is a reference to the prototype object of the person object, which is the object from which the person object inherits properties and methods.

The prototype property of the Person function is the object that is used as the prototype for all objects created with the Person function.

Because the person object was created with the Person function, its prototype object will be the prototype property of the Person function. Therefore, the comparison in the code will return true.

 

Please explain the following code of js:

function Person() {

}
console.log(Person === Person.prototype.constructor); // true

 

The code that you provided compares the Person function with the constructor property of the prototype object of the Person function.

Here's a step-by-step explanation of what the code is doing:

1. The Person function is defined like this:

    
2. function Person() { }

   This is a simple function that doesn't take any arguments and doesn't have a body. It is intended to be used as a constructor function, which means that it will be used to create new objects.

3. The Person function is compared to the constructor property of the prototype object of the Person function like this:

    

console.log(Person === Person.prototype.constructor); // true

This statement compares the Person function with the constructor property of the prototype object of the Person function.

The constructor property is a reference to the function that was used to create the prototype object.

In this case, the prototype object of the Person function was created using the Person function, so the constructor property of the prototype object will be a reference to the Person function.

Therefore, the comparison in the code will return true.

 

作者:Chuck Lu    GitHub