


Learn JavaScript design patterns template method pattern_javascript skills
1. Definition
The template method is based on the inheritance design pattern, which can greatly improve the scalability of the system. Abstract parent class and subclass in java
The template method consists of two parts of the structure, the first part is the abstract parent class, and the second part is the concrete implementation subclass.
2. Example
Coffee or Tea
(1) Boil water
(2) Soak tea leaves in boiling water
(3) Pour the tea into the cup
(4) Add lemon
/* 抽象父类:饮料 */ var Beverage = function(){}; // (1) 把水煮沸 Beverage.prototype.boilWater = function() { console.log("把水煮沸"); }; // (2) 沸水浸泡 Beverage.prototype.brew = function() { throw new Error("子类必须重写brew方法"); }; // (3) 倒进杯子 Beverage.prototype.pourInCup = function() { throw new Error("子类必须重写pourInCup方法"); }; // (4) 加调料 Beverage.prototype.addCondiments = function() { throw new Error("子类必须重写addCondiments方法"); }; /* 模板方法 */ Beverage.prototype.init = function() { this.boilWater(); this.brew(); this.pourInCup(); this.addCondiments(); } /* 实现子类 Coffee*/ var Coffee = function(){}; Coffee.prototype = new Beverage(); // 重写非公有方法 Coffee.prototype.brew = function() { console.log("用沸水冲泡咖啡"); }; Coffee.prototype.pourInCup = function() { console.log("把咖啡倒进杯子"); }; Coffee.prototype.addCondiments = function() { console.log("加牛奶"); }; var coffee = new Coffee(); coffee.init();
Using the template method pattern, the algorithm framework of the subclass is encapsulated in the parent class. These algorithm frameworks are suitable for most subcategories under normal circumstances, but "personality" subcategories will also appear.
As in the above process, adding seasonings is optional.
The hook method can solve this problem. Placing hooks is a common means of isolating changes.
/* 添加钩子方法 */ Beverage.prototype.customerWantsCondiments = function() { return true; }; Beverage.prototype.init = function() { this.boilWater(); this.brew(); this.pourInCup(); if(this.customerWantsCondiments()) { this.addCondiments(); } } /* 实现子类 Tea*/ var Tea = function(){}; Tea.prototype = new Beverage(); // 重写非公有方法 Tea.prototype.brew = function() { console.log("用沸水冲泡茶"); }; Tea.prototype.pourInCup = function() { console.log("把茶倒进杯子"); }; Tea.prototype.addCondiments = function() { console.log("加牛奶"); }; Tea.prototype.customerWantsCondiments = function() { return window.confirm("需要添加调料吗?"); }; var tea = new Tea(); tea.init();
JavaScript does not provide true class inheritance. Inheritance is achieved through delegation between objects.
3. "Hollywood Principle": Don't call us, we will call you
Typical usage scenarios:
(1) Template method pattern: Using this design pattern means that the subclass gives up control of itself and instead informs the subclass to the parent class. As a subclass, it is only responsible for providing some design details.
(2) Observer mode: The publisher pushes the message to the subscribers.
(3) Callback function: ajax asynchronous request encapsulates the operations that need to be performed in the callback function. This callback function is only executed when the data is returned.
I hope this article will be helpful to everyone learning JavaScript programming.

JavaScript originated in 1995 and was created by Brandon Ike, and realized the language into C. 1.C language provides high performance and system-level programming capabilities for JavaScript. 2. JavaScript's memory management and performance optimization rely on C language. 3. The cross-platform feature of C language helps JavaScript run efficiently on different operating systems.

JavaScript runs in browsers and Node.js environments and relies on the JavaScript engine to parse and execute code. 1) Generate abstract syntax tree (AST) in the parsing stage; 2) convert AST into bytecode or machine code in the compilation stage; 3) execute the compiled code in the execution stage.

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.

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.

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 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 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.

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.


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