Interpretation of examples of creating objects and inheritance in JavaScript_javascript skills

Object creation:

When a function object is created, the function object generated by the Function constructor will run code similar to this:

Copy code The code is as follows:

this.prototype={constructor:this};

Assume function F
F constructs the object using new method When the object's constructor is set to this F.prototype.constructor
If the function modifies the prototype of the function before creating the object, it will affect the constructor attribute of the created object

For example:

Copy code The code is as follows:

function F(){};
F.prototype={constructor: '1111'};
var o=new F();//o.constructor==='1111' true

Principle of inheritance:

Inheritance in JavaScript It is a mechanism that uses the prototype chain. Each function instance shares the data defined in the prototype attribute of the constructor. To make one class inherit another, the parent function instance needs to be assigned to the prototype attribute of the child function. And every time a new instance object is created, the object's private property __proto__ will be automatically connected to the prototype of the constructor.

instanceof is to look up the private prototype attribute chain of the instance object to determine whether it is an instance of the specified object

Specific example:

Copy code The code is as follows:

//instanceof implements
function Myinstanceof(obj,type)
{
var proto=obj.__proto__;
while(proto)
{
if(proto ===type.prototype)break;
proto=proto.__proto__;
}
return proto!=null;
}


function View(){}
function TreeView(){}
TreeView.prototype=new View();//TreeView.prototype.__proto__=TreeView.prototype automatic completion
TreeView.prototype.constructor=TreeView;//Correction constructor
var view=new TreeView();//view.__proto__=TreeView.prototype automatically completed
alert(view instanceof View); //true When view.__proto__.__proto__ is found,
alert(view instanceof TreeView); //true is found. When view.__proto__ is found,
alert(Myinstanceof(view,View)); //true
alert(Myinstanceof(view,TreeView)); //true