What is JavaScript modularity and its advantages and disadvantages Introduction _ Basics

Now backbone, Emberjs, Spinejs, Batmanjs and other MVC frameworks have come to the attack. Commonjs, AMD, Nodejs, Requirejs, Seajs, Curljs and other modular JavaScript are coming. Web front-end has evolved into a large front-end, the Web front-end development faster.

1 Let's see what modularity is?
Modularization is a method of separating the system into independent functional parts, which can be divided into separate functional parts, which strictly define the transparency between module interfaces and modules. Modules in JavaScript are more common in some C, PHP, and Java:

C uses include. h files, PHP uses require_once to include. php files
Java Import package using Import
There are modular ideas in this.

2 The advantages and disadvantages of modularity:

A> Advantages:
Maintainability
1. Flexible architecture, focus separation
2. Easy to combine and decompose between modules
3. Facilitate single module function debugging, upgrade
4. Multi-person collaboration and mutual interference
Testability
1. Can be divided into unit test

B> Disadvantages:
Performance loss
1. System layering, call chain will be very long
2. Communication between modules, sending messages between modules can be very performance-consuming

3 Recent projects also useful to the modular, the use of SEAJS, but when referencing to the Jquery,jquery easyui/or jquery UI components, it is possible to use a lot of jquery plug-ins, so if you implement a very complex interaction, the dependencies between the modules will be much, Using the Define () method to introduce modules will be a lot, do not know what is the best way?

4) Attached:
Cohesion degree
Cohesion refers to the internal implementation of the module, which is the natural extension of the concept of information hiding and localization, which indicates the close degree of the integration of each component within a module. The benefits are also obvious, and it is much easier to read the relevant tasks when grouped. Design should be as much as possible to improve the cohesion of the module, so as to obtain higher module independence.

Coupling degree
Coupling degree refers to the measurement of the degree of association between modules. The degree of coupling depends on the complexity of the interface between modules, the position of the module entering or calling. In contrast to cohesion, a loosely coupled system should be pursued as far as possible in design.