


Introduction to JavaScript Pattern Factory Pattern Application_Javascript Skills
Factory pattern is also one of the object creation patterns. It is usually implemented in a class or a static method of a class. One way to construct an object is to use the new operator, but using new is precisely for implementation programming, which will cause "coupling" problems and is closely related to the specific class. This makes the code more fragile and lacks flexibility. In projects with complex logic, it is recommended to interface-oriented programming.
Look at the simple factory pattern first
Person(name, age) {
var obj = {}
obj.name = name
obj.age = age
return obj
}
var p1 = Person('jack', 25)
var p2 = Person('lily', 22)
The difference between writing a class in the constructor way is that you do not use this, but construct an empty object every time and then give it Add properties. The way to create an object is not to use new, but to use function calling. This approach is basically used to replace a class (objects with the same properties), while more complex factories can create different types of objects.
The following is an example of a fruit factory
function Banana( ) {
this.price = '$1.5'
}
function Apple() {
this.price = '$1.2'
}
function Orange() {
this .price = '$2.2'
}
// Static factory class
function Fruit() {}
Fruit.factory = function(type) {
if (!window[type]) {
return
}
var fruit = new window[type]
return fruit
}
// Make different fruits
var banana = Fruit.factory('Banana ')
var apple = Fruit.factory('Apple')
var orange = Fruit.factory('Orange')
There are three fruit classes Banana, Apple, and Orange, one The fruit factory class Fruit can create different fruit objects each time through the static method factory.
The factory pattern is also reflected in the JavaScript native object Object, such as
var obj = Object(),
num = Object(1),
str = Object('s'),
boo = Object(false);
Object is a factory, which will construct different objects according to different parameters. obj is an empty object, num is a Number type object, str is a String type object, and boo is a Boolean type object.
jQuery.Callbacks is also a factory. Each time it is called, it will return an object with methods such as add, remove, fire, etc. Objects with different properties can also be constructed based on parameters such as "once", "memory", etc.
The so-called factory pattern refers to a method that can return an object.
What can we do using this model? Suppose I am not satisfied with the methods in the existing DOM objects and I want to add a custom method called sayHello. We can do this:
function RemouldNodeObj(DomNode){
//First determine whether the parameter passed in is a Dom node
if(typeof DomNode == "object" && DomNode.nodeType == 1){
DomNode.say = function(){
alert("Hello!!");
}
}else{
alert("The parameters you passed in are incorrect!");
}
}
//Call like this:
window.onload = function(){
var oDiv = RemouldNodeObj(document.getElementById("test"));
//With this step, oDiv has a new method say
oDiv.say();
}
After having the above foundation, let's implement some complex functions. We want to generate a simple form by calling js. Look at the code:
Did you see it? Is this calling method very similar to jQuery? If we can solve the cross-browser problem, we can actually make a search bar plug-in!

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.

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.

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.

JavaScript's application in the real world includes front-end and back-end development. 1) Display front-end applications by building a TODO list application, involving DOM operations and event processing. 2) Build RESTfulAPI through Node.js and Express to demonstrate back-end applications.


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