Understanding the JavaScript prototype chain

Every JavaScript object is associated with another object, and the associated object is what we call a "prototype". Every object inherits properties and methods from the prototype. There is a special object that does not have a prototype, which is Object. This will be explained in the following illustrations.

For example, we first declare a function Student():

function Student(name){
  this.name = name;
 this.hello = function(){
   alert(`Hello,${this.name}`);
 }
 }

This function contains an attribute name and a method hello.
In JavaScript, you can call the Student function through the new keyword (without writing new it is a normal function, writing new is a constructor), and returns an object whose prototype points to Student.prototype, as shown below:

var xiaoming = new Student("xiaoming");
alert(xiaoming.name); // xiaoming
xiaoming.hello(); // Hello,xiaoming

If we want to confirm whether our assumption is correct, we will want to compare whether xiaoming.prototype and Student.prototype are equal.
But xiaoming does not have a prototype attribute, but you can use __proto__ to view it. Next, we will use these attributes to view the prototype chain between xiaoming, Student, and Object:

document.onreadystatechange = function(){
 // interactive表示文档已被解析，但浏览器还在加载其中链接的资源
 if(document.readyState === "interactive"){
  var xiaoming = new Student("xiaoming");
  alert(xiaoming.name);
  xiaoming.hello();
  console.log("xiaoming.__proto__：");
  console.log(xiaoming.__proto__);
  console.log("Student.prototype：");
  console.log(Student.prototype);
  console.log("xiaoming.__proto__ === Student.prototype：" + xiaoming.__proto__ === Student.prototype);
  console.log("Student.prototype.constructor：" + Student.prototype.constructor);
  console.log("Student.prototype.prototype：" + Student.prototype.prototype);
  console.log("Student.prototype.__proto__：");
  console.log(Student.prototype.__proto__);
  console.log(Object.prototype);
  console.log("Student.prototype.__proto__ === Object.prototype：" + Student.prototype.__proto__ === Object.prototype);
 }
}