JavaScript的对象文字与控制台记录时似乎命名的对象有什么区别？

Question

I have noticed there are times when I console.log an object, I get the object literal and sometimes its seems what is console.logged is prefixed with a name.

For example, If I console.log an object before sending it to the server I get:

{id: 18, date: "2017-09-13T21:59:59.999Z"...etc}

but when I console the same log returned as a promise from a server call, I get:

Resource {id: 18, date: "2017-09-13T21:59:59.999Z"...etc}

What causes this differences? and What are the differences between what seems to be two different representations of an object?

Answer 1

它们有一个constructor属性，它不指向Object ，但在这种情况下指向Ressource 。

Answer 2

The console is giving you hints, it doesn't always log stuff as is.

For example:

var Cat = function (name) {
    this.name = name;
}

var paws = new Cat('paws');
console.log(paws);

will act similar to Resource in your example. The console is hinting at the constructor .

Answer 3

The latter is an instance of a named class:

class Resource {
   constructor() {
      this.id = ...;
      this.date = ...;
   }
}

Or a named constructor:

function Resource() {
  this.id = ...;
  this.date = ...;
}

In both cases, the class or constructor in instantiated with the new keyword, but class is the newer ES6 syntax.

console.log(new Resource())

Your first example is simply a plain object with no constructor.