Home > Articles

This chapter is from the book

Working with Node Packages

One of the most powerful features of the Node.js framework is the ability to easily extend it with additional Node Packaged Modules (NPMs) using the Node Package Manager (NPM). That’s right, in the Node.js world, NPM stands for two things. This book refers to the Node Packaged Modules as modules to make it easier to follow.

What Are Node Packaged Modules?

A Node Packaged Module is a packaged library that can easily be shared, reused, and installed in different projects. Many different modules are available for a variety of purposes. For example, the Mongoose module provides an ODM (Operational Data Model) for MongoDB, Express extends Node’s HTTP capabilities, and so on.

Node.js modules are created by various third-party organizations to provide the needed features that Node.js lacks out of the box. This community of contributors is active in adding and updating modules.

Node Packaged Modules include a package.json file that defines the packages. The package.json file includes informational metadata, such as the name, version author, and contributors, as well as control metadata, such as dependencies and other requirements that the Node Package Manager uses when performing actions such as installation and publishing.

Understanding the Node Package Registry

The Node modules have a managed location called the Node Package Registry where packages are registered. This allows you to publish your own packages in a location where others can use them as well as download packages that others have created.

The Node Package Registry is located at https://npmjs.com. From this location you can view the newest and most popular modules as well as search for specific packages, as shown in Figure 3.1.

Figure 3.1

Figure 3.1 The official Node Package Modules website

Using the Node Package Manager

The Node Package Manager you have already seen is a command-line utility. It allows you to find, install, remove, publish, and do everything else related to Node Package Modules. The Node Package Manager provides the link between the Node Package Registry and your development environment.

The simplest way to really explain the Node Package Manager is to list some of the command-line options and what they do. You use many of these options in the rest of this chapter and throughout the book. Table 3.1 lists the Node Package Manager commands.

Table 3.1 npm command-line options (with express as the package, where appropriate)

Option Description Example
search Finds module packages in the repository npm search express
install Installs a package either using a package.json file, from the repository, or a local location npm install
npm install express
npm install express@0.1.1
npm install ../tModule.tgz
install –g Installs a package globally npm install express -g
remove Removes a module npm remove express
pack Packages the module defined by the package.json file into a .tgz file npm pack
view Displays module details npm view express
publish Publishes the module defined by a package.json file to the registry npm publish
unpublish Unpublishes a module you have published npm unpublish myModule
owner Allows you to add, remove, and list owners of a package in the repository npm add bdayley myModule
npm rm bdayley myModule
npm ls myModule

Searching for Node Package Modules

You can also search for modules in the Node Package Registry directly from the command prompt using the npm search <search_string> command. For example, the following command searches for modules related to openssl and displays the results as shown in Figure 3.2:

npm search openssl
Figure 3.2

Figure 3.2 Searching for Node.js modules from the command prompt

Installing Node Packaged Modules

To use a Node module in your applications, it must first be installed where Node can find it. To install a Node module, use the npm install <module_name> command. This downloads the Node module to your development environment and places it into the node_modules folder where the install command is run. For example, the following command installs the express module:

npm install express

The output of the npm install command displays the dependency hierarchy installed with the module. For example, the following code block shows part of the output from installing the express module.

C:\express\example
`-- express@4.14.0
  +-- accepts@1.3.3
  | +-- mime-types@2.1.11
  | | `-- mime-db@1.23.0
  | `-- negotiator@0.6.1
  +-- array-flatten@1.1.1
  +-- content-disposition@0.5.1
  +-- content-type@1.0.2
  +-- cookie@0.3.1
  +-- cookie-signature@1.0.6
  +-- debug@2.2.0
  | `-- ms@0.7.1 ...

The dependency hierarchy is listed; some of the methods Express requires are cookie-signature, range-parser, debug, fresh, cookie, and send modules. Each of these was downloaded during the install. Notice that the version of each dependency module is listed.

Node.js has to be able to handle dependency conflicts. For example, the express module requires cookie 0.3.1, but another module may require cookie 0.3.0. To handle this situation, a separate copy for the cookie module is placed in each module’s folder under another node_modules folder.

To illustrate how modules are stored in a hierarchy, consider the following example of how express looks on disk. Notice that the cookie and send modules are located under the express module hierarchy, and that since the send module requires mime it is located under the send hierarchy:

./
./node_modules
./node_modules/express
./node_modules/express/node_modules/cookie
./node_modules/express/node_modules/send
./node_modules/express/node_modules/send/node_modules/mime

Using package.json

All Node modules must include a package.json file in their root directory. The package.json file is a simple JSON text file that defines the module including dependencies. The package.json file can contain a number of different directives to tell the Node Package Manager how to handle the module.

The following is an example of a package.json file with a name, version, description, and dependencies:

{
    "name": "my_module",
    "version": "0.1.0",
    "description": "a simple node.js module",
    "dependencies" : {
        "express"   :  "latest"
    }
}

The only required directives in the package.json file are name and version. The rest depend on what you want to include. Table 3.2 describes the most common directives:

Table 3.2 Directives used in the package.json file

Directive Description Example
name Unique name of package. "name": "camelot"
preferGlobal Indicates this module prefers to be installed globally. "preferGlobal": true
version Version of the module. "version": 0.0.1
author Author of the project. "author": "arthur@???.com"
description Textual description of module. "description": "a silly place"
contributors Additional contributors to the module.
"contributors": [
  { "name": "gwen",
    "email": "gwen@???.com"}]
bin Binary to be installed globally with project.
"bin: {
    "excalibur":
"./bin/excalibur"}
scripts Specifies parameters that execute console apps when launching node.
"scripts" {
    "start": "node ./bin/
excalibur",
    "test": "echo testing"}
main Specifies the main entry point for the app. This can be a binary or a .js file. "main": "./bin/excalibur"
repository Specifies the repository type and location of the package.
"repository": {
    "type": "git",
    "location":
    "http://???.com/c.git"}
keywords Specifies keywords that show up in the npm search.
"keywords": [
  "swallow", "unladen" ]
dependencies Modules and versions this module depends on. You can use the * and x wildcards.
"dependencies": {
   "express": "latest",
   "connect": "2.x.x,
   "cookies": "*" }
engines Version of node this package works with.
"engines": {
   "node": ">=6.5"}

A great way to use package.json files is to automatically download and install the dependencies for your Node.js app. All you need to do is create a package.json file in the root of your project code and add the necessary dependencies to it. For example, the following package.json requires the express module as a dependency.

{
    "name": "my_module",
    "version": "0.1.0",
    "dependencies" : {
        "express"  :  "latest"
    }
}

Then you run the following command from root of your package, and the express module is automatically installed.

npm install

Notice that no module is specified in the npm install. That is because npm looks for a package.json file by default. Later, as you need additional modules, all you need to do is add those to the dependencies directive and then run npm install again.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020