Easy-to-understand analysis of JS prototypes and prototype chains
This time I will bring you an easy-to-understand analysis of JS prototypes and prototype chains. What are the precautions for analyzing JS prototypes and prototype chains? Here are practical cases, let’s take a look.
Objects in Browser
What objects are there in the browser? In ES, the global object is global, while in browsers, the global object is window.
Enter window in the chrome console, and we can see what is in the window.
The following objects can be found in window.
Attributes such as Object, Sring, Numbr, Boolean, Array, Date, Math, parseInt, parseFloat are all required objects specified by ES.
Such as document, alert, prompt, atob, etc. These are the attributes built into the browser.
These objects all have hash structures, such as Object and String, which have their own properties and methods , and corresponding API calls.
Simple types and objects
The examples are as follows: n1 is a simple type and n2 is an object.
var n1 = 'a'var n2 = new String('a') n1.length n1.hasOwnProperty('0') n2.length n2.hasOwnProperty('0') n1.xxx = 2n1.xxx // undefined
Difference
The n1 value is stored in the stack. When n2 is assigned, an address is created in the stack, pointing to the heap, and a new String type object is created in the heap memory. You can see that there are some attributes in object n2, as well as the prototype attribute.
Attribute
n2 is an object with a length attribute, so it is called. n1 is just a string, why does it also have a length attribute?
can be understood like this: when n1.length, js will perform the following operations: var temp = new String(n1);n1.length ;That is, when using attributes or methods, a new object will be temporarily created in the heap memory. This object is of the corresponding String type. After execution, temp will be destroyed. Therefore, the n1.xxx = 2 operation will not report an error, but n1.xxx displays undefined again, because the data of n1 in the heap memory has been destroyed at this time.
Therefore, in js, the new method of a new object is rarely used, but the variable is assigned directly. hasOwnProperty()
hasOwnProperty() in
n2 is a method in the Object class type. It is not found under the Sting type. Where can I find it?
Here hasOwnProperty() is in n2.proto.proto. n2.proto points to String.prototype, and String.prototype.proto finally points to Object.prototype. String is a prototype, and Object is also a prototype. Object.prototype stores all public properties of the Object type.
In this way, it can effectively save space and avoid recording many attributes in each object. For attributes that are not found in an object, search for them in the object pointed to by proto. The point pointed to is usually the prototype of a certain prototype.
Where to find proto and prototype
var n = new Number(1)var s= new String('1')var o= new Object()
The above methods can be regarded as the form of var object = function ().
In summary, object.proto = function.prototype.
Access proto
Proto is relative to the object. Find the father to see who generated the object. For n, the father is Number, so go to Number.prototype to find it. There is also proto in Number. When accessing, look for it in its parent Object.
Function String.proto === Function.prototype //true
Functions can also be regarded as objects. String, Object, and Number are all objects and functions. Because new String() was used before, this is a function, and the data type of the function return result is object. String's father is Function.
Function.proto === Function.prototype //trueFunction.prototype.proto === Object.prototype //trueFunction.proto.proto === Object.prototype //true
When Function is regarded as an object generated by the Function method,
that is, var Function = new Function()
can understand Function.proto == = Function.prototype
The type of Fuction is function, which is constructed from Function. The relationship can be seen from the picture above. When new String(), the type of String is also function, and String.proto points to Function.prototype.
I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!
Recommended reading:
How to avoid features and browser inference in JS
Detailed explanation of JS facade pattern use cases
The above is the detailed content of Easy-to-understand analysis of JS prototypes and prototype chains. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
A deep dive into the meaning and usage of HTTP status code 460
Feb 18, 2024 pm 08:29 PM
In-depth analysis of the role and application scenarios of HTTP status code 460 HTTP status code is a very important part of web development and is used to indicate the communication status between the client and the server. Among them, HTTP status code 460 is a relatively special status code. This article will deeply analyze its role and application scenarios. Definition of HTTP status code 460 The specific definition of HTTP status code 460 is "ClientClosedRequest", which means that the client closes the request. This status code is mainly used to indicate
iBatis and MyBatis: Comparison and Advantage Analysis
Feb 18, 2024 pm 01:53 PM
iBatis and MyBatis: Differences and Advantages Analysis Introduction: In Java development, persistence is a common requirement, and iBatis and MyBatis are two widely used persistence frameworks. While they have many similarities, there are also some key differences and advantages. This article will provide readers with a more comprehensive understanding through a detailed analysis of the features, usage, and sample code of these two frameworks. 1. iBatis features: iBatis is an older persistence framework that uses SQL mapping files.
Detailed explanation of Oracle error 3114: How to solve it quickly
Mar 08, 2024 pm 02:42 PM
Detailed explanation of Oracle error 3114: How to solve it quickly, specific code examples are needed. During the development and management of Oracle database, we often encounter various errors, among which error 3114 is a relatively common problem. Error 3114 usually indicates a problem with the database connection, which may be caused by network failure, database service stop, or incorrect connection string settings. This article will explain in detail the cause of error 3114 and how to quickly solve this problem, and attach the specific code
Parsing Wormhole NTT: an open framework for any Token
Mar 05, 2024 pm 12:46 PM
Wormhole is a leader in blockchain interoperability, focused on creating resilient, future-proof decentralized systems that prioritize ownership, control, and permissionless innovation. The foundation of this vision is a commitment to technical expertise, ethical principles, and community alignment to redefine the interoperability landscape with simplicity, clarity, and a broad suite of multi-chain solutions. With the rise of zero-knowledge proofs, scaling solutions, and feature-rich token standards, blockchains are becoming more powerful and interoperability is becoming increasingly important. In this innovative application environment, novel governance systems and practical capabilities bring unprecedented opportunities to assets across the network. Protocol builders are now grappling with how to operate in this emerging multi-chain
Analysis of the meaning and usage of midpoint in PHP
Mar 27, 2024 pm 08:57 PM
[Analysis of the meaning and usage of midpoint in PHP] In PHP, midpoint (.) is a commonly used operator used to connect two strings or properties or methods of objects. In this article, we’ll take a deep dive into the meaning and usage of midpoints in PHP, illustrating them with concrete code examples. 1. Connect string midpoint operator. The most common usage in PHP is to connect two strings. By placing . between two strings, you can splice them together to form a new string. $string1=&qu
Analysis of new features of Win11: How to skip logging in to Microsoft account
Mar 27, 2024 pm 05:24 PM
Analysis of new features of Win11: How to skip logging in to a Microsoft account. With the release of Windows 11, many users have found that it brings more convenience and new features. However, some users may not like having their system tied to a Microsoft account and wish to skip this step. This article will introduce some methods to help users skip logging in to a Microsoft account in Windows 11 and achieve a more private and autonomous experience. First, let’s understand why some users are reluctant to log in to their Microsoft account. On the one hand, some users worry that they
Apache2 cannot correctly parse PHP files
Mar 08, 2024 am 11:09 AM
Due to space limitations, the following is a brief article: Apache2 is a commonly used web server software, and PHP is a widely used server-side scripting language. In the process of building a website, sometimes you encounter the problem that Apache2 cannot correctly parse the PHP file, causing the PHP code to fail to execute. This problem is usually caused by Apache2 not configuring the PHP module correctly, or the PHP module being incompatible with the version of Apache2. There are generally two ways to solve this problem, one is
Analysis of exponential functions in C language and examples
Feb 18, 2024 pm 03:51 PM
Detailed analysis and examples of exponential functions in C language Introduction: The exponential function is a common mathematical function, and there are corresponding exponential function library functions that can be used in C language. This article will analyze in detail the use of exponential functions in C language, including function prototypes, parameters, return values, etc.; and give specific code examples so that readers can better understand and use exponential functions. Text: The exponential function library function math.h in C language contains many functions related to exponentials, the most commonly used of which is the exp function. The prototype of exp function is as follows
