node web development 2nd edition: chapter3 node modules

Node ModulesRick Chang

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

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!'

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

Module identifiers

Module identifiers: relative, absolute, top-level

relative

./, ../,

absolute

begin with /

top-level

node_modules directory

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

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

System-wide modules

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

Package format

package.json is followed by CommonJS Pacakge/1.0 specification

The documentation of package.json

npm help json

Dependency

Package format

“dependencies": { "foo" : "1.0.0 – 2.x.x", "bar" : ">=1.0.2 <2.1.2"}

Executable commandbin: { 'nodeload.js': './nodeload.js', 'nl.js': './nl.js'}

Package formatDescribe 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

NPM

Search package

npm search [packagename]

Public package repository

https://www.npmjs.org

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

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

NPM

Eliminate the duplicate modules

npm deduce

List your installed packages

npm list

npm list -g

NPM

Go the folder of the installed package

npm explore express

npm explore express -g

Build your package

Initial your package to build the skeleton

npm init

name: (tmod2) version: (0.0.0) 0.0.1description: this is test moduleentry point: (index.js) test command: git repository: keywords: test, learnauthor: Rick Changlicense: (ISC) MITAbout 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"}

Build your package

Before publishing your package, test it

npm link

Create a symbolic link in your system-wide modules

Publish

npm publish

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]

Configuration settings

List your configuration settings

npm config list

Delete the key

npm config delete [key]

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