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This article will explain in detail what the Object in JavaScript is, and the content of the article is of high quality, so the editor will share it with you for reference. I hope you will have a certain understanding of the relevant knowledge after reading this article.

What exactly is the Object of JavaScript?

At first I thought Object was the prototype of all the objects in js.

But: alert (Object.constructor) displays function Function...

This means that the prototype of Object is Function?

But here comes the problem again:

Function.prototype.read=function () {}; / / extend the prototype of Function

For (var i in Object) alert (I) / / shows read, which further confirms that the prototype of Object is Function

Object.prototype.read=function () {}; / / extends the prototype of Object

For (var i in Function) alert (I) / shows that the prototype of read,Function is Object????

What on earth is Object? Is Object and Function the same thing as a class?

This friend confused Constructor, Prototype and Function, because JavaScript is the language of Object-based (JavaScript does not contain proper classes). It is OK to say that Object is the prototype of all objects, but this refers to the prototype concept in Prototype Pattern in the design pattern, not Object.prototype, the prototype language feature of JavaScript.

So what exactly is Object in JavaScript? Script56.chm (the official tutorial on M$) says: provides functionality common to all JScript objects. Yeah, do you understand? Because I should understand, but the friendly elephant still doesn't understand @ _ @. In terms of data structure, an object (an instance of Object) is an unordered collection, similar to the structure of map in C++, hashtable in C#, and hashmap in Java. And contains a primitive value given by the JavaScript language system. What does that mean? Object has a method called valueOf, which returns the original value of the specified object. This can also be found in Script56, and there is also a table listing the valueOf return results of system objects. In other words, Array, Boolean, Date, Function, Number and other objects are all from Object, and their ancestors are all Object. They represent different language features, such as Array has automatically managed length attributes, Boolean has only true or false values, Date represents time structure, and Function can be run, all of which are given to them by their original types (valueOf). Object is really just a concept. JavaScript, a language based on objects, means that all built-in types are abstracted from a common set of methods and properties (also called behaviors and states). We imagine that the only thing that has these features is Object. In fact, Object is not very useful in programming, we are all using the instance object of Object, and then using the collection feature of Object (expando), extending object becomes what we want. For Object.prototype, it's not really useful, because each exact type has its own prototype, and most of the prototyping methods we add are for certain types.

In addition to prototype, Object has another very important attribute-constructor. This thing is used to complete the extension of object that I mentioned earlier, and it is also the basis for us to use JavaScript to simulate OOP. Because everything in JavaScript is Object, so is constructor, but its primitive type is Function (run Object.constructor.valueOf () to get: function Function () {[native code]}). Of course, conversely, not all JavaScript objects have constructor properties, and some built-in objects do not have constructor.

For the relationship between Object and Function, I don't think this is a good test code: Function.prototype.read=function () {}; / / extend the prototype of Function

For (var i in Object) alert (I) / / shows read, which further confirms that the prototype of Object is Function

Object.prototype.read=function () {}; / / extend the prototype of Object

For (var i in Function) alert (I) / shows that the prototype of read,Function is Object?

These four lines of code are used to explain the principle of JavaScript's prototype and compare sexy with the prototype inheritance method that simulates OO programming. But they do not clearly explain the relationship between Object and Function: (instead, they will fool audiovisual.

Here is a brief description of the various object types in JavaScript:

Native Object: objects provided by the JavaScript language that do not depend on the execution host, some of which are built-in objects, such as Global and Math;, are created and used in the script runtime environment, such as Array, Boolean, Date, Function, Number, Object, RegExp, Error.

Build-in Object: JavaScript language provides built-in objects that do not depend on the execution host, such as: Global, Math; built-in objects are Native Object.

Any object provided by the Host Object:JavaScript language that depends on the host environment, all objects that are not Native Object are host objects, such as wscript instances in window,WScript in IE, any user-created classes

So much for sharing what Object is in JavaScript. I hope the above content can be helpful to everyone and learn more knowledge. If you think the article is good, you can share it for more people to see.

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