Cause
An important reason for organizing code into classes is to make the code more "modular" and enable code reuse in many different scenarios. But classes are not the only way to modularize code.
Generally speaking, a module is an independent JS file. A module file can contain a class definition, a set of related classes, a library of utility functions, or some code to be executed.
The goal of modularization is to support large-scale program development, handle the assembly of code from dispersed sources, and enable the code to run correctly, even if it contains unnecessary module code.
Ideally, no module should define more than one global flag.
Module function
is implemented by defining the module inside a function. The defined variables and functions are local variables of the function and are not visible outside the function. In fact, you can use this function scope as the module’s namespace (module function)
Once the module code is encapsulated into a function, you need some way to export the public API so that they can be called outside the module function. There are several ways to export public APIs:
First create a namespace
// Create a global variable to store school-related information Module
var school; // Create school namespace
if(!school) school = {};
1. Use constructor
// Return the Student constructor to export the public API
school.Student = (function() {
function Student() {
}
//... Define the prototype object and private properties and methods of Student.... ....
return Student; // Return Student constructor to export public API
})();
2. Return the namespace object
If the module API includes multiple units, it can return a namespace object
// Add students module to school
school. students = (function() {
// Many classes are defined here such as course class/grade class, using local variables and functions
function Subject() { /* ... */ }
function Grade () { /* ... */ }
// Export the API by returning the namespace object
return {
Subject: Subject,
Grade: Grade
};
})();
3. Call
through the keyword newAnother similar technique: treat module functions as constructors and call them through new. Assign them (public API) to this attribute to export them
school.students = (new function() {
// ..... The code is omitted here...
// Direct the API to this object
this.Subject = Subject;
this.Grade = Grade ;
// Note that there is no return value here
}()); // The brackets are written inside. Here is the creation of a new instance. New should be followed by a call to the constructor instead of an expression
4. Defined namespace object
As an alternative, if a global namespace object has been defined, module functions can directly set the properties of that object.
// If the namespace object has been defined
var school; // Create school namespace
if(!school) school = {};
school.students = {}; // The student namespace has been defined
(function(students) {
// ..... The code is omitted here...
// Direct the public API to it In the defined namespace
students.Subject = Subject;
students.Grade = Grade;
// There is no need to return a value here
})(school.students);
For this reason, the method of exporting public API has been explained.

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.

The main uses of JavaScript in web development include client interaction, form verification and asynchronous communication. 1) Dynamic content update and user interaction through DOM operations; 2) Client verification is carried out before the user submits data to improve the user experience; 3) Refreshless communication with the server is achieved through AJAX technology.

Understanding how JavaScript engine works internally is important to developers because it helps write more efficient code and understand performance bottlenecks and optimization strategies. 1) The engine's workflow includes three stages: parsing, compiling and execution; 2) During the execution process, the engine will perform dynamic optimization, such as inline cache and hidden classes; 3) Best practices include avoiding global variables, optimizing loops, using const and lets, and avoiding excessive use of closures.

Python is more suitable for beginners, with a smooth learning curve and concise syntax; JavaScript is suitable for front-end development, with a steep learning curve and flexible syntax. 1. Python syntax is intuitive and suitable for data science and back-end development. 2. JavaScript is flexible and widely used in front-end and server-side programming.

Python and JavaScript have their own advantages and disadvantages in terms of community, libraries and resources. 1) The Python community is friendly and suitable for beginners, but the front-end development resources are not as rich as JavaScript. 2) Python is powerful in data science and machine learning libraries, while JavaScript is better in front-end development libraries and frameworks. 3) Both have rich learning resources, but Python is suitable for starting with official documents, while JavaScript is better with MDNWebDocs. The choice should be based on project needs and personal interests.

The shift from C/C to JavaScript requires adapting to dynamic typing, garbage collection and asynchronous programming. 1) C/C is a statically typed language that requires manual memory management, while JavaScript is dynamically typed and garbage collection is automatically processed. 2) C/C needs to be compiled into machine code, while JavaScript is an interpreted language. 3) JavaScript introduces concepts such as closures, prototype chains and Promise, which enhances flexibility and asynchronous programming capabilities.


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