search
HomeWeb Front-endJS TutorialJavaScript design patterns factory pattern and constructor pattern_javascript skills

What is a pattern

I was preparing for the final exam a while ago. It was so tiring and tiring, and I really didn’t have time to update the article. Today I will talk to you about the design patterns in JavaScript.

First of all, what we need to know is: a pattern is a reusable solution, while an anti-pattern is a poor solution to a certain problem.

Common examples of js anti-patterns

1. Pass strings to setTimeout and setInterval instead of functions, which triggers the internal use of eval().
2. Define a large number of variables in the global context to pollute the global namespace
3. Modify the prototype of the Object class
4. Use js in inline form. The js code embedded in the HTML file cannot be included in external unit testing tools.
5. Abusing document.write. If document.write is executed after the page is loaded, it will rewrite the page we are on. If you can use document.creatElement instead, try not to use document.write.

Categories of design patterns

Creative Design Pattern

Creative design patterns focus on handling object creation mechanisms to create objects in a way that is appropriate for a given situation. Properties that fall into this category include:

Constructor, Factory, Abstract, Prototype, Singleton and Builder

Structural Design Pattern

Structural patterns are about object composition and can often be used to find simple ways to establish relationships between different objects.
Patterns that fall into this category include:

Decorator, Facade appearance, Flyweight, Adapter adapter and Proxy agent

Behavioral Design Patterns

Behavioral patterns focus on improving or simplifying communication between different objects in the system.

Behavior patterns include:

Iterator, Mediator, Observer and Visitor

Factory mode

In order to solve the problem of multiple similar object declarations, we can use a method called factory pattern. This method is to solve the problem of a large number of duplications when instantiating objects.

Copy code The code is as follows:


Classification of Factory Pattern

Factory mode is divided into simple factory, abstract factory and smart factory. Factory mode does not require the use of a constructor explicitly.

Simple Factory Pattern: Use a class (usually a singleton) to generate instances.
Complex factory pattern: Use subclasses to determine which specific class instance a member variable should be.

Benefits of Factory Model

The main benefit is that you can eliminate the coupling between objects by using engineering methods instead of the new keyword. Prevent code duplication by centralizing all instantiation code in one location.
Disadvantages of factory model

For most classes, it is best to use the new keyword and constructor, which can make the code simpler and easier to read. Rather than having to look at the factory method to find out. 
The factory pattern solves the problem of repeated instantiation, but there is another problem, that is, the problem of identification, because it is impossible to figure out which object they are instances of.

Copy code The code is as follows:

alert(typeof test1); //Object
alert(test1 instanceof Object); //true

When to use factory pattern?

Factory mode is mainly used in the following scenarios:

1. When objects or components involve high complexity
2. When you need to easily generate different instances of an object according to different environments
3. When dealing with many small objects or components that share the same properties

Constructor pattern

Constructor (constructor method) can be used in ECMAScript to create specific objects. This mode can just solve the problem that the above factory mode cannot identify object instances.

Copy code The code is as follows:


Using the constructor method not only solves the problem of repeated instantiation, but also solves the problem of object recognition. The difference between this mode and the factory mode is:

1. The constructor method does not create an object explicitly (new Object());
2. Directly assign properties and methods to this object;
3. There is no renturn statement.

There are some specifications for constructor methods:

1. The function name and the instantiation constructor name are the same and capitalized (PS: It is not mandatory, but writing this way helps distinguish the constructor from the ordinary function);
2. To create an object through a constructor, you must use the new operator.
Since objects can be created through constructors, where does this object come from, and where is new Object() executed? The execution process is as follows:

1. When a constructor is used and new constructor() is used, new Object() is executed in the background;
2. Give the scope of the constructor to the new object (that is, the object created by new Object()), and this in the function body represents the object created by new Object().
3. Execute the code within the constructor;
4. Return the new object (return directly in the background).

Constructor with prototype

There is an attribute called prototype in js. After calling the js constructor to create an object, the new object will have all the properties of the constructor prototype. In this way, multiple Car objects can be created and have access to the same prototype.

Copy code The code is as follows:



Now a single instance of run() can be shared among all Car objects.
Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
The Future of Python and JavaScript: Trends and PredictionsThe Future of Python and JavaScript: Trends and PredictionsApr 27, 2025 am 12:21 AM

The future trends of Python and JavaScript include: 1. Python will consolidate its position in the fields of scientific computing and AI, 2. JavaScript will promote the development of web technology, 3. Cross-platform development will become a hot topic, and 4. Performance optimization will be the focus. Both will continue to expand application scenarios in their respective fields and make more breakthroughs in performance.

Python vs. JavaScript: Development Environments and ToolsPython vs. JavaScript: Development Environments and ToolsApr 26, 2025 am 12:09 AM

Both Python and JavaScript's choices in development environments are important. 1) Python's development environment includes PyCharm, JupyterNotebook and Anaconda, which are suitable for data science and rapid prototyping. 2) The development environment of JavaScript includes Node.js, VSCode and Webpack, which are suitable for front-end and back-end development. Choosing the right tools according to project needs can improve development efficiency and project success rate.

Is JavaScript Written in C? Examining the EvidenceIs JavaScript Written in C? Examining the EvidenceApr 25, 2025 am 12:15 AM

Yes, the engine core of JavaScript is written in C. 1) The C language provides efficient performance and underlying control, which is suitable for the development of JavaScript engine. 2) Taking the V8 engine as an example, its core is written in C, combining the efficiency and object-oriented characteristics of C. 3) The working principle of the JavaScript engine includes parsing, compiling and execution, and the C language plays a key role in these processes.

JavaScript's Role: Making the Web Interactive and DynamicJavaScript's Role: Making the Web Interactive and DynamicApr 24, 2025 am 12:12 AM

JavaScript is at the heart of modern websites because it enhances the interactivity and dynamicity of web pages. 1) It allows to change content without refreshing the page, 2) manipulate web pages through DOMAPI, 3) support complex interactive effects such as animation and drag-and-drop, 4) optimize performance and best practices to improve user experience.

C   and JavaScript: The Connection ExplainedC and JavaScript: The Connection ExplainedApr 23, 2025 am 12:07 AM

C and JavaScript achieve interoperability through WebAssembly. 1) C code is compiled into WebAssembly module and introduced into JavaScript environment to enhance computing power. 2) In game development, C handles physics engines and graphics rendering, and JavaScript is responsible for game logic and user interface.

From Websites to Apps: The Diverse Applications of JavaScriptFrom Websites to Apps: The Diverse Applications of JavaScriptApr 22, 2025 am 12:02 AM

JavaScript is widely used in websites, mobile applications, desktop applications and server-side programming. 1) In website development, JavaScript operates DOM together with HTML and CSS to achieve dynamic effects and supports frameworks such as jQuery and React. 2) Through ReactNative and Ionic, JavaScript is used to develop cross-platform mobile applications. 3) The Electron framework enables JavaScript to build desktop applications. 4) Node.js allows JavaScript to run on the server side and supports high concurrent requests.

Python vs. JavaScript: Use Cases and Applications ComparedPython vs. JavaScript: Use Cases and Applications ComparedApr 21, 2025 am 12:01 AM

Python is more suitable for data science and automation, while JavaScript is more suitable for front-end and full-stack development. 1. Python performs well in data science and machine learning, using libraries such as NumPy and Pandas for data processing and modeling. 2. Python is concise and efficient in automation and scripting. 3. JavaScript is indispensable in front-end development and is used to build dynamic web pages and single-page applications. 4. JavaScript plays a role in back-end development through Node.js and supports full-stack development.

The Role of C/C   in JavaScript Interpreters and CompilersThe Role of C/C in JavaScript Interpreters and CompilersApr 20, 2025 am 12:01 AM

C and C play a vital role in the JavaScript engine, mainly used to implement interpreters and JIT compilers. 1) C is used to parse JavaScript source code and generate an abstract syntax tree. 2) C is responsible for generating and executing bytecode. 3) C implements the JIT compiler, optimizes and compiles hot-spot code at runtime, and significantly improves the execution efficiency of JavaScript.

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

PhpStorm Mac version

PhpStorm Mac version

The latest (2018.2.1) professional PHP integrated development tool

mPDF

mPDF

mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),

MinGW - Minimalist GNU for Windows

MinGW - Minimalist GNU for Windows

This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

MantisBT

MantisBT

Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

EditPlus Chinese cracked version

EditPlus Chinese cracked version

Small size, syntax highlighting, does not support code prompt function