js中的模块和php中的类有什么区别？

Question

I am learning about modules online and it seems like modules in js and classes in php are very similar. Both group functions together for easier to understand coding. Functions can be declared in both and made public or private. How are they similar in use and how are they different?

Answer 1

Javascript's modules provides some nice features like encapsulation, the private state and even inheritance from other modules. While they provide some of the features of classes, as in PHP, they are not. They try to build on the existing Javascript functonality to emulate classes, hence why the confusion. ie they are built to look and feel like classes .

Javascript's modules are instances of an anonymous function assigned to a variable. Therefore they have all the features of a function where their code is executed top to bottom, they have and sometimes use a return statement (in PHP classes no statements can be run directly apart from field definition and assignment) and they even have access to global variables . In PHP, on the other hand a class, or rather it's methods, cannot access a variable that is not in the class itself. In order to access global variables a class method or static function has to explicitly call the variable ie global $a inorder to import it. In js modules, all global vars are accessible but sometimes one chooses to explicity import them for neater code (function(a){})(imported);

Another important issue is data abstraction. While js modules provide private states for the fields, PHP's classes, just like C++, java, python etc, provide more security to the properties. It allows for base classes using the abstract class and interface keywords whereby class methods and attributes are only defined or structured but not used.

PHP classes also have constructors and destructors, that are called when the class object is initialized and on the last mention used to destroy the object. Granted, you can create functions in modules to run when you want, in PHP on the other hand, functions in the method are only executed when they are called either by the object, the class or other functions.

In classes there are static functions, these can be called without even having an object of the class and run independent of objects, on the other hand in js, everything is an object; which defeats the point of static functions.

They are similar in that: both have inheritance, where you can extend an existing module with a new one, and in PHP you can use extends to inherit from a parent class. They both have private data states preventing external access, they both group and package data and methods, and both are awesome when utilized properly.