javascript local properties, inherited properties, prototype chain

1. Javascript has own properties , and some properties are inherited from prototype objects, called inherited properties .

   function Obj() {
         
         
   	this.x = 10;		// 本地属性 own property
   }
   Obj.prototype.x = 0;	// 继承属性
   Obj.prototype.y = 1;	// 继承属性
   
   let o = new Obj();
   console.log(o)
   

   The print result is as follows:
   
2. Prototype chain
   Suppose you want to query the attribute y of object o, if y does not exist in the local attribute, then it will continue to search for attribute y in the prototype object of o. If there is no y in the prototype object, but the prototype object also has a prototype, then continue to perform the query on the prototype of the prototype object until y is not found or an object whose prototype is null is found. The prototype properties of the object form a "chain". The inheritance of attributes can be achieved through this "chain".
   • Find inherited properties on the prototype chain console.log(o.y) // 1
   • Local attributes will block inherited attributes with the same nameconsole.log(o.x) // 10
   • When adding an attribute of a basic data type, if it has the same name as the inherited attribute, a new local attribute independent of the inherited attribute will be automatically created o.y = 20; console.log(Obj.prototype.y) // 1
   • If the inherited attribute is a reference data type, modifying its value will affect the attribute on the prototype

   Obj.prototype.list = [1,2,3];
   o.list[0] = 0;
   console.log(Obj.prototype.list); // [0, 2, 3]
   

3. Three methods of attribute detection
4. Three methods of property traversal

How to better understand the own properties and prototypal inheritance properties of Javascript objects