Node module concept and npm commands

1. Node Modules
Rick Chang

2. Modules
One module per .js file
Objects not assigned to exports are not
visible to any code outside the module
The globals in a module are actually
local to that module
Called module encapsulation

3. Module
simple.js using require()
var count = 0;
exports.next = function() {
return count++;
}
!
exports.hello = function() {
return "Hello, World!";
}
$ node
> var s = require('./simple');
undefined
> s.next()
0
> s.next()
1
> s.next()
2
> s.hello()
'Hello, World!'

4. Module encapsulation
module1.js module2.js
24 Jul 15:41:32 - A = a different value A,
B = a different value B, values = { A: 'value A', B: 'value B' }
var util = require("util");
var m1 = require("./module1");
!
var A = "a different value A";
var B = "a different value B";
!
util.log('A = ' + A + ', B = ' + B + ',
values = ' + util.inspect(m1.values()));
var A = "value A";
var B = "value B";
exports.values = function() {
return {
A : A,
B : B
};
};
Result

5. Module identifiers
Module identifiers: relative, absolute, top-level
relative
./, ../,
absolute
begin with /
top-level
node_modules directory

6. node_modules Hierarchy
Node searches the node_modules in the
current directory
If not found, move to the parent directory
until it reaches the root of the file system.
System-wide modules

7. node_modules Hierarchy
/home/david/projects/drawapp/lib/node_modules
/home/david/projects/drawapp/node_modules
/home/david/projects/node_modules
/home/david/node_modules
/home/node_modules
/node_modules

8. System-wide modules
All system-wide modules in /$
{NODE_HOME}/lib/node_modules

9. Package format
package.json is followed by CommonJS
Pacakge/1.0 specification
The documentation of package.json
npm help json

10. Dependency
Package format
“dependencies": {
"foo" : "1.0.0 – 2.x.x",
"bar" : ">=1.0.2 <2.1.2"
}
Executable command
bin: {
'nodeload.js': './nodeload.js',
'nl.js': './nl.js'
}

11. Package format
Describe directory structure
directories: { lib: './lib', bin: './bin' }
"scripts": {
"prepublish": "npm prune",
"test": "mocha --require test/support/env --reporter dot
--check-leaks test/ test/acceptance/"
}
Run scripts in the life cycle of the package,
which include install, activate, uninstall, update
The documentation
npm help scripts

12. NPM
Search package
npm search [packagename]
Public package repository
https://www.npmjs.org

13. NPM
Show the whole package.json
npm view [packagename]
Show the specific attributes of the package.json
npm view express dependencies
npm view express author
npm view express repository.url

14. NPM
Install package in system-wide modules
npm install -g express
Install package with the specific version in current
directory
npm install express@3.15.0
Uninstall package
npm uninstall express

15. NPM
Eliminate the duplicate modules
npm deduce
List your installed packages
npm list
npm list -g

16. NPM
Go the folder of the installed package
npm explore express
npm explore express -g

17. Build your package
Initial your
package to build
the skeleton
npm init
name: (tmod2)
version: (0.0.0) 0.0.1
description: this is test module
entry point: (index.js)
test command:
git repository:
keywords: test, learn
author: Rick Chang
license: (ISC) MIT
About to write to xxx/ch3/tmod2/package.json:
!
{
"name": "tmod2",
"version": "0.0.1",
"description": "this is test module",
"main": "index.js",
"scripts": {
"test": "echo "Error: no test specified" && exit 1"
},
"keywords": [
"test",
"learn"
],
"author": "Rick Chang",
"license": "MIT"
}

18. Build your package
Before publishing your package, test it
npm link
Create a symbolic link in your system-wide
modules
Publish
npm publish

19. Configuration settings
All configuration settings are in ${HOME}/.npmrc or <Node
Install Directory>/etc/npmrc
Get the config value
npm get [key]
npm config get [key]
Change the config vale
npm set [key value]
npm config set [key value]

20. Configuration settings
List your configuration settings
npm config list
Delete the key
npm config delete [key]

21. Configuration settings
Enable color mode to show npm data
npm set color true
Enable parse mode to show npm data
npm set parseable true
Enable global mode to install packages in system-wide
npm set global true