Node.js: It is a JavaScript runtime(server-side) built on V8 JavaScript engine of Google Chrome. It was developed in 2009 by Ryan Dhal. Node.js uses an event-driven, non-blocking input/output model that makes it lightweight and efficient. It is perfect for placeholder='Add your personal notes here! (max 5000 chars)'>
This tutorial concludes the series on npm's cli command. In the previous tutorial we showed you how to npm-version as well as the npm update commands. This tutorial will cover how you can view the info of a registry as well as the display your npm username. The npm-view will help you view information about a registry. The version number is in syntax which designates each section with different meaning. Syntax is broken into three sections separated by a dot. Major.minor.patch 1.0.2. Major, minor and patch represent the different releases of a package. Npm uses the tilde and caret (^) to designate which patch and minor versions to use respectively.
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Free clipper (gclip for mac. npm is awesome as a package manager. In particular, it handles sub-dependencies very well: if my package depends on
request
version 2 and some-other-library
, but some-other-library
depends on request
version 1, the resultingdependency graph looks like:This is, generally, great: now
some-other-library
has its own copy of request
v1 that it can use, while notinterfering with my package's v2 copy. Saitek pro flight instrument panel plugin for mac. Everyone's code works!The Problem: Plugins
There's one use case where this falls down, however: plugins. A plugin package is meant to be used with another 'host'package, even though it does not always directly use the host package. There are many examples of this pattern in theNode.js package ecosystem already:
- Grunt plugins
- Chai plugins
- LevelUP plugins
- Express middleware
- Winston transports
Even if you're not familiar with any of those use cases, surely you recall 'jQuery plugins' from back when you were aclient-side developer: little
<script>
s you would drop into your page that would attach things to jQuery.prototype
for your later convenience.In essence, plugins are designed to be used with host packages. But more importantly, they're designed to be used withparticular versions of host packages. For example, versions 1.x and 2.x of my
chai-as-promised
plugin work withchai
version 0.5, whereas versions 3.x work with chai
1.x. Or, in the faster-paced and less-semver–friendly world ofGrunt plugins, version 0.3.1 of grunt-contrib-stylus
works with grunt
0.4.0rc4, but breaks when used with grunt
0.4.0rc5 due to removed APIs.As a package manager, a large part of npm's job when installing your dependencies is managing their versions. But itsusual model, with a
'dependencies'
hash in package.json
, clearly falls down for plugins. Most plugins never actuallydepend on their host package, i.e. grunt plugins never do require('grunt')
, so even if plugins did put down their hostpackage as a dependency, the downloaded copy would never be used. So we'd be back to square one, with your applicationpossibly plugging in the plugin to a host package that it's incompatible with.Even for plugins that do have such direct dependencies, probably due to the host package supplying utility APIs,specifying the dependency in the plugin's
package.json
would result in a dependency tree with multiple copies of thehost package—not what you want. For example, let's pretend that winston-mail
0.2.3 specified 'winston': '0.5.x'
inits 'dependencies'
hash, since that's the latest version it was tested against. As an app developer, you want thelatest and greatest stuff, so you look up the latest versions of winston
and of winston-mail
, putting them in yourpackage.json
asBut now, running
npm install
results in the unexpected dependency graph ofI'll leave the subtle failures that come from the plugin using a different Winston API than the main application toyour imagination.
Npm Install
The Solution: Peer Dependencies
What we need is a way of expressing these 'dependencies' between plugins and their host package. Some way of saying, 'Ionly work when plugged in to version 1.2.x of my host package, so if you install me, be sure that it's alongside acompatible host.' We call this relationship a peer dependency.
The peer dependency idea has been kicked around for literallyyears. Google chrome mac os x 10.5 8 download. Aftervolunteering to get this done 'over the weekend' ninemonths ago, I finally found a free weekend, and now peer dependencies are in npm!
Specifically, they were introduced in a rudimentary form in npm 1.2.0, and refined over the next few releases intosomething I'm actually happy with. Today Isaac packaged up npm 1.2.10 intoNode.js 0.8.19, so if you've installed the latest version ofNode, you should be ready to use peer dependencies!
As proof, I present you the results of trying to install
jitsu
0.11.6 with npm1.2.10:As you can see,
jitsu
depends on two Flatiron-related packages, which themselves peer-depend on conflicting versionsof Flatiron. Good thing npm was around to help us figure out this conflict, so it could be fixed in version 0.11.7!Using Peer Dependencies
Peer dependencies are pretty simple to use. When writing a plugin, figure out what version of the host package youpeer-depend on, and add it to your
package.json
:Now, when installing
chai-as-promised
, the chai
package will come along with it. And if later you try to installanother Chai plugin that only works with 0.x versions of Chai, you'll get an error. Nice!UPDATE: npm versions 1 and 2 will automatically install peerDependencies if they are not explicitly depended upon higher in the dependency tree. For all following versions of npm (starting with [email protected]), this will no longer be the case. You will receive a warning that the peerDependency is not installed instead.
One piece of advice: peer dependency requirements, unlike those for regular dependencies, should be lenient. Youshould not lock your peer dependencies down to specific patch versions. It would be really annoying if one Chai pluginpeer-depended on Chai 1.4.1, while another depended on Chai 1.5.0, simply because the authors were lazy and didn't spendthe time figuring out the actual minimum version of Chai they are compatible with.
Package Json Dependencies Syntax
The best way to determine what your peer dependency requirements should be is to actually followsemver. Assume that only changes in the host package's major version will break your plugin. Thus,if you've worked with every 1.x version of the host package, use
'~1.0'
or '1.x'
to express this. If you depend onfeatures introduced in 1.5.2, use '>= 1.5.2 < 2'
.Npm Package Versioning
Now go forth, and peer depend! Introduction to the study of the ten sefirot pdf file.