Commonjs,amd,cmd specification

1. Javascript inherently lacks the functionality of the module. In other high-level languages, Java has a class file, Python has an import mechanism, Ruby has require,php include and require, and JavaScript needs to rely on <script> tags to introduce code, When the script is many, it will appear disorganized.

2. In response to the above problems, Commonjs emerged. COMMONJS has a vision for javascript: to be able to run anywhere! (not just for browser), Commonjs wants to make up for JavaScript without standard flaws (no modular system, fewer standard libraries, no standard interfaces, no package management system), and can write large applications such as server-side JavaScript, command-line tools, Desktop graphical interface applications, hybrid applications, and more.

3. The CommONJS specification covers:

module, binary Buffer , Character set encoding, I/O flow, process environment, file system, sockets, Web Server network Management interface, package administration and so on.

4. Node. JS follows the COMMONJS specification and advances the development of Commonjs .

5. CommOnjs is mainly for JS in the back end of the performance of the formulation, not suitable for the front end. Why do you say that?

The front-end JavaScript is placed on both ends of the HTTP , each of which plays a different role:

	browser-side Java Script	Server-Side Java Script
Execution of code	Need to experience distribution from the same server side to multiple client executions	The same code needs to be executed multiple times
Bottleneck	is the bandwidth	is that CPU and Memory Resources
How code is loaded	Need to load code over the network	Load code from disk (both speed not at one order of magnitude)

6. AMD appeared,Asynchronous module definition. Asynchronous module definitions.

It is mainly for the front-end JS performance Norm .

AMD specification has only one API , its module is defined as follows:

DeFine (id?,dependencies?,factory);//id,dependencies optional, factory content is the content of the actual code.

A. ID: module identification, can be omitted, here the module identifier refers to itself, that is, the entire file. So when the ID is omitted, it is equivalent to defining an anonymous module, when the module filename is the module identifier. e.g. the module file is placed in A.js, then A is the module name.

B. dependencies: Dependency module. the AMD specification specifies all dependencies when declaring the module, and also as a parameter to the factory . For example:

define ([' Dep1 ', ' dep2 '], function (DEP1, DEP2) {...});

An example that does not include a dependency relationship:

define (function () {

var exports = {};

Exports.method = function () {...};

return exports;

...

});

c.  from d Span style= "line-height:0px;" > efine function is not difficult to think of define The function has an asynchronous nature. When it executes, it first asynchronously invokes the dependent module listed in the second parameter, and executes if the third parameter is a callback function when all the modules are loaded.

D. in node. js , you don't see the define module wrapped up because node The implicit packaging is implemented (i.e. when the module is at compile time,nodemodules are packaged to isolate each module file to prevent variable contamination).

E. Requirejs is the implementation of the AMD specification.

7. The CMD specification is presented by the Yuber in the country and differs from the AMD specification in the definition of modules and dependencies introduced in the section. The style is closer to Node. You can look at sea.js.

Commonjs,amd,cmd specification