Relationship between prototype, prototype chain, constructor and instance

As shown in the figure ：

1.instanceof Detect the relationship between constructor and instance ：

function Person () {.........}

person = new Person ()

res = person instanceof Person

res  // true

2. The instance inherits the defined properties on the prototype ：

function Person () {........}

Person.prototype.type = 'object n'

person = new Person ()

res = person.type

res  // object n

3. Instance access ===> Prototype

Case passed __proto__ Visit the prototype person.proto=== Person.prototype

4. Prototype access ===> Constructors

Prototypes pass constructor Property access constructor Person.prototype.constructor === Person

5. Instance access ===> Constructors

person.proto.constructor === Person

Two 、 Prototype chain
In the process of reading the properties of an instance , If the attribute is not found in this instance , Then it will follow proto Search for the specified prototype , If you can't find , Then look for the prototype of the prototype ：

1. Find on instance

function Person() {}

    Person.prototype.type = "object name Person";

    person = new Person();

    person.type = " I am the own attribute of the instance ";

    res = Reflect.ownKeys(person); // Try to get your own attributes 

    console.log(res);

    res = person.type;

    console.log(res); // I am the own attribute of the instance （ Search up through the prototype chain and give priority to the search in the instance ）

2. Look for on the prototype

function Person() {}

    Person.prototype.type = "object name Person";

    person = new Person();

    res = Reflect.ownKeys(person); // Try to get your own attributes 

    console.log(res);

    res = person.type;

    console.log(res); //object name Person

3. Look for the prototype of the prototype

function Person() {}

    Person.prototype.type = "object name Person";

    function Child() {}

    Child.prototype = new Person();

    p = new Child();

    res = [p instanceof Object, p instanceof Person, p instanceof Child];

    console.log(res); //[true, true, true] p Belong to at the same time Object,Person, Child

    res = p.type; // Layer by layer search 

    console.log(res); //object name Person ( Search on the prototype chain )

    console.dir(Person);

    console.dir(Child);

4. Search on the prototype chain

1. Prototypes can also be passed proto Access the prototype of the prototype , For example, here is a constructor Child then “ Inherit ” The former has a constructor Person, then new Child Get an example p;

2. When accessing p When a non self owned attribute in , Would pass proto As a series of prototypes connected by bridges 、 The prototype of the prototype 、 Prototype prototype prototype until Object So far ;

3. Prototype chain search found null until , If you can't find the accessed attribute, stop ：

function Person() {}

  Person.prototype.type = "object name Person";

  function Child() {}

  Child.prototype = new Person();

  p = new Child();

  res = p.__proto__;

  console.log(res);         //Person {}

  res = p.__proto__.__proto__;

  console.log(res);         //Person {type:'object name Person'}

  res = p.__proto__.__proto__.__proto__;

  console.log(res);         //{.....}

  res = p.__proto__.__proto__.__proto__.__proto__;

  console.log(res);         //null