Explanation of js prototype

2 min readJun 28, 2020

The constructor creates the object

function  Person () {

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

Person is a constructor, we use new to create an instance object person

prototype

Every function has a prototype property.
Every JavaScript object (except null) will be associated with another object when it is created. This object is what we call a prototype, and each object will “inherit” properties from the prototype.

function  Person () {

} 
//Although it is written in a comment,
//but you should pay attention: 
// prototype is a property that only functions have.
Person.prototype.name = 'Aditya' ; 
var person1 = new Person(); 
var person2 = new Person(); 
console .log(person1.name) // Aditya
console .log(person2.name) // Aditya

proto

Every JavaScript object (except null) has a property called proto , which will point to the prototype of the object

function  Person () {

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

constructor

Each prototype has a constructor attribute that points to the associated constructor instance. The prototype points to the constructor.

function Person() {
}
console.log(Person === Person.prototype.constructor); // truefunction Person() {

}

var person = new Person ();

console .log(person.__proto__ == Person.prototype) // true 
console .log(Person.prototype.constructor == Person) // true 
console .log( Object .getPrototypeOf(person) === Person.prototype) // true

Examples and prototypes

function  Person () {

}

Person.prototype.name = 'Aditya';

var person = new Person ();

person.name = 'Daisy';
console.log(person.name) // Daisy

delete person.name;
console.log(person.name) // Aditya

In this example, we added the name attribute to the instance object person. When we print person.name, the result is naturally Daisy. But when we removed the person’s name attribute, read person.name, will not find the name attribute is the person. From the person from the person’s prototype object proto, which is a Person. prototype Look, fortunately, we Found the name attribute, the result is Aditya.