Dynamic installation and loading of Node.js module [closed] - javascript

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I am working on a Node.js module A that uses another Node.js module B from NPM. There are new versions of module B published on NPM. I want my module A to dynamically update to the latest versions of module B (module A always depends on the latest version of module B).Also, all the references of the imported module should also be updated dynamically.
I considered using NPM programmatically to install the latest available version of a module if a module is outdated. Are there better solutions to do this dynamically.
Also, how to forcefully update the module references imported through require?
Thanks!

At least to the first part of your question (module A always using the latest version of module B), you could always specify the dependency in your package.json with a major version wildcard:
{
"dependencies": {
"moduleB": "*"
}
}
Which would then allow you to always npm update to the latest version. (This would, however, potentially have the effect of introducing changes that break backwards compatibility in your module as npm uses Semantic Versioning.)
As for running npm update automatically, I have to ask - why is this necessary? What would be the benefit to users of your module? You should be, at the very least, "curating" updates to your dependencies to ensure no breaking changes are introduced. If you did set up a full automatic pipeline for updating dependencies (from npm updateing dependencies to git taging new versions to npm versioning these new versions to npm publishing these new versions, for example), you're sort of leaving users of your module out in the cold should any of these steps break compatibility with their code.
(Also, if this automatic dependency updating never breaks your module, then what is your module adding? Is it even doing anything non-trivial with the dependencies?)
It might seem cumbersome, but it's a better practice to update your dependencies with some craft and intention. See Semantic Versioning for more info.

Related

Can I automatically clean deprecated #types/ packages?

I'm upgrading an old typescript project. Many years ago, most packages had corresponding #types packages. Nowadays, typings are usually included in the main package, therefore typing packages got obsolete.
A typical example is yup. Many years ago it needed #types/yup, but now it's deprecated.
I have 30+ typing packages in my project, and because I don't want to manually clean them, I'm asking:
What if I just leave them in pakages.json? I guess there is a big chance they would mislead typescript and IDE, right?
Is there a command or script to list or clean deprecated packages?

Is it worth the trouble to commit package-lock.json? [closed]

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I have a NodeJS project published on GitHub that uses a few NPM modules, as specified in my package.json. I have my package-lock.json committed into the repo.
Recently I got notices on my repository about a recently-discovered security vulnerability in one of my dependencies. Upon further inspection, it wasn't one of my direct dependencies that had a vulnerability but rather a module that one of my dependencies is dependent on. Because all the modules show up in my package-lock.json, the notice comes up telling me to update that dependency to the latest version.
- myproject
- someDependency
- anotherDependency
- aSubDependency
- anotherOne <--- this one has a security issue
So now I have to question: Is it worth committing a package-lock.json? I wouldn't have any security vulnerabilities in my project if I didn't have a package-lock.json. Now, I am forced to update my project and republish simply to update the package-lock.json. If that file wasn't there at all, the problem would fix itself because anyone who does an install or update of my project using ONLY the package.json would automatically get the updated dependency from up the stream.
Think about it like this. Bob creates moduleA. Then someone else creates moduleB that is dependent on moduleA. Then 1000 developers out in the world create various projects that directly are dependent on moduleB. If Bob discovers a security vulnerability in moduleA, now 1000 people have to make an update to their 1000 projects just to fix this all because they were committing their package-lock.json.
So it is worth it? Do the advantages of package-lock.json outweigh the drawbacks in this topic?
Yes, it worth
This file is intended to be committed into source repositories, and
serves various purposes:
Describe a single representation of a dependency tree such that
teammates, deployments, and continuous integration are guaranteed to
install exactly the same dependencies.
Provide a facility for users to “time-travel” to previous states of
node_modules without having to commit the directory itself.
To facilitate greater visibility of tree changes through readable
source control diffs.
And optimize the installation process by allowing npm to skip repeated
metadata resolutions for previously-installed packages.
See npm documentation
See GitHub - "Viewing and updating vulnerable dependencies in your repository"

Do you bundle your library for user to import, or let them import the source? [closed]

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You write libraries using ES6/7, so someone importing the source would have to use Webpack + Babel to transpile the code.
You can get around that problem by providing the transpiled bundle. But then the problem is you would bundle in your dependencies, which the user may also have. Then the dependency gets bundled in redundantly for the user.
You want to preserve the
import MyLib from 'my-lib'
syntax so you don't want to provide two import paths.
What do you do?
You should just bundle your library. Even if the user happens to use the same dependencies that you use, most likely they will be using a different version, which might not work with your library.
If you want to reduce the size of your bundle, you should use Rollup.js—it uses tree-shaking, which basically means that your bundle will include only the parts of the code that you actually need.
After digging around, I found an excellent example:
https://github.com/reactjs/redux
Redux uses package.json prepublish to transpile the source code, without bundling it. This works perfectly as it no longer requires the user of the library to use babel, and at the same time does not bundle in dependencies.

Why npm was written in JavaScript? [closed]

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I looked into npm's package.json file and discovered that npm is actually just a node.js package which has a lot of dependencies such as lodash. This means the situation that happened with left-pad package that broke a lot of npm packages could affect npm too.
I see that there is some tendency: pip is written in python, RubyGems in Ruby, Composer in PHP, Maven in Java and so on. But is it good to write a package manager in the target language?
More specifically npm was written using npm - JavaScript has nothing to do the npm leftpad incident. I can't imagine them not using their own product for several reasons:
It's a tool for managing software dependencies. They must use one. Would you propose they use someone else's? Of course, if you trust your product you're going to use it yourself.
The leftpad "incident" was a policy flaw more than a software flaw which they obviously did not predict or consider to be a serious concern until something serious happened. Therefore, why would this be a reason not to use npm.
Of the hundreds of thousands of packages hosted it can't have happened too often or it would have been fixed long ago. That's quite impressive.
It was pretty easy to fix just be updating the caching policy and so it's not a threat to npm.
Other package management tools have had similar problems (or worse). For example, an entire maven repository went offline due to lack of funding. This is unlikely to happen to npm because it is centralized and there are many large stakeholders who are interested in making sure it stays up.
Incidents like these make the ecosystem more stable and mature.
Like all stories, this will blow over in no time.
The very reason is that npm is the default package manager for the JavaScript runtime environment Node.js
It is natural for the package manager to be written in the language of its runtime.

What is the difference between Bower and npm?

What is the fundamental difference between bower and npm? Just want something plain and simple. I've seen some of my colleagues use bower and npm interchangeably in their projects.
All package managers have many downsides. You just have to pick which you can live with.
History
npm started out managing node.js modules (that's why packages go into node_modules by default), but it works for the front-end too when combined with Browserify or webpack.
Bower is created solely for the front-end and is optimized with that in mind.
Size of repo
npm is much, much larger than bower, including general purpose JavaScript (like country-data for country information or sorts for sorting functions that is usable on the front end or the back end).
Bower has a much smaller amount of packages.
Handling of styles etc
Bower includes styles etc.
npm is focused on JavaScript. Styles are either downloaded separately or required by something like npm-sass or sass-npm.
Dependency handling
The biggest difference is that npm does nested dependencies (but is flat by default) while Bower requires a flat dependency tree (puts the burden of dependency resolution on the user).
A nested dependency tree means that your dependencies can have their own dependencies which can have their own, and so on. This allows for two modules to require different versions of the same dependency and still work. Note since npm v3, the dependency tree will be flat by default (saving space) and only nest where needed, e.g., if two dependencies need their own version of Underscore.
Some projects use both: they use Bower for front-end packages and npm for developer tools like Yeoman, Grunt, Gulp, JSHint, CoffeeScript, etc.
Resources
Nested Dependencies - Insight into why node_modules works the way it does
This answer is an addition to the answer of Sindre Sorhus. The major difference between npm and Bower is the way they treat recursive dependencies. Note that they can be used together in a single project.
On the npm FAQ: (archive.org link from 6 Sep 2015)
It is much harder to avoid dependency conflicts without nesting
dependencies. This is fundamental to the way that npm works, and has
proven to be an extremely successful approach.
On Bower homepage:
Bower is optimized for the front-end. Bower uses a flat dependency
tree, requiring only one version for each package, reducing page load
to a minimum.
In short, npm aims for stability. Bower aims for minimal resource load. If you draw out the dependency structure, you will see this:
npm:
project root
[node_modules] // default directory for dependencies
-> dependency A
-> dependency B
[node_modules]
-> dependency A
-> dependency C
[node_modules]
-> dependency B
[node_modules]
-> dependency A
-> dependency D
As you can see it installs some dependencies recursively. Dependency A has three installed instances!
Bower:
project root
[bower_components] // default directory for dependencies
-> dependency A
-> dependency B // needs A
-> dependency C // needs B and D
-> dependency D
Here you see that all unique dependencies are on the same level.
So, why bother using npm?
Maybe dependency B requires a different version of dependency A than dependency C. npm installs both versions of this dependency so it will work anyway, but Bower will give you a conflict because it does not like duplication (because loading the same resource on a webpage is very inefficient and costly, also it can give some serious errors). You will have to manually pick which version you want to install. This can have the effect that one of the dependencies will break, but that is something that you will need to fix anyway.
So, the common usage is Bower for the packages that you want to publish on your webpages (e.g. runtime, where you avoid duplication), and use npm for other stuff, like testing, building, optimizing, checking, etc. (e.g. development time, where duplication is of less concern).
Update for npm 3:
npm 3 still does things differently compared to Bower. It will install the dependencies globally, but only for the first version it encounters. The other versions are installed in the tree (the parent module, then node_modules).
[node_modules]
dep A v1.0
dep B v1.0
dep A v1.0 (uses root version)
dep C v1.0
dep A v2.0 (this version is different from the root version, so it will be an nested installation)
For more information, I suggest reading the docs of npm 3
TL;DR: The biggest difference in everyday use isn't nested dependencies... it's the difference between modules and globals.
I think the previous posters have covered well some of the basic distinctions. (npm's use of nested dependencies is indeed very helpful in managing large, complex applications, though I don't think it's the most important distinction.)
I'm surprised, however, that nobody has explicitly explained one of the most fundamental distinctions between Bower and npm. If you read the answers above, you'll see the word 'modules' used often in the context of npm. But it's mentioned casually, as if it might even just be a syntax difference.
But this distinction of modules vs. globals (or modules vs. 'scripts') is possibly the most important difference between Bower and npm. The npm approach of putting everything in modules requires you to change the way you write Javascript for the browser, almost certainly for the better.
The Bower Approach: Global Resources, Like <script> Tags
At root, Bower is about loading plain-old script files. Whatever those script files contain, Bower will load them. Which basically means that Bower is just like including all your scripts in plain-old <script>'s in the <head> of your HTML.
So, same basic approach you're used to, but you get some nice automation conveniences:
You used to need to include JS dependencies in your project repo (while developing), or get them via CDN. Now, you can skip that extra download weight in the repo, and somebody can do a quick bower install and instantly have what they need, locally.
If a Bower dependency then specifies its own dependencies in its bower.json, those'll be downloaded for you as well.
But beyond that, Bower doesn't change how we write javascript. Nothing about what goes inside the files loaded by Bower needs to change at all. In particular, this means that the resources provided in scripts loaded by Bower will (usually, but not always) still be defined as global variables, available from anywhere in the browser execution context.
The npm Approach: Common JS Modules, Explicit Dependency Injection
All code in Node land (and thus all code loaded via npm) is structured as modules (specifically, as an implementation of the CommonJS module format, or now, as an ES6 module). So, if you use NPM to handle browser-side dependencies (via Browserify or something else that does the same job), you'll structure your code the same way Node does.
Smarter people than I have tackled the question of 'Why modules?', but here's a capsule summary:
Anything inside a module is effectively namespaced, meaning it's not a global variable any more, and you can't accidentally reference it without intending to.
Anything inside a module must be intentionally injected into a particular context (usually another module) in order to make use of it
This means you can have multiple versions of the same external dependency (lodash, let's say) in various parts of your application, and they won't collide/conflict. (This happens surprisingly often, because your own code wants to use one version of a dependency, but one of your external dependencies specifies another that conflicts. Or you've got two external dependencies that each want a different version.)
Because all dependencies are manually injected into a particular module, it's very easy to reason about them. You know for a fact: "The only code I need to consider when working on this is what I have intentionally chosen to inject here".
Because even the content of injected modules is encapsulated behind the variable you assign it to, and all code executes inside a limited scope, surprises and collisions become very improbable. It's much, much less likely that something from one of your dependencies will accidentally redefine a global variable without you realizing it, or that you will do so. (It can happen, but you usually have to go out of your way to do it, with something like window.variable. The one accident that still tends to occur is assigning this.variable, not realizing that this is actually window in the current context.)
When you want to test an individual module, you're able to very easily know: exactly what else (dependencies) is affecting the code that runs inside the module? And, because you're explicitly injecting everything, you can easily mock those dependencies.
To me, the use of modules for front-end code boils down to: working in a much narrower context that's easier to reason about and test, and having greater certainty about what's going on.
It only takes about 30 seconds to learn how to use the CommonJS/Node module syntax. Inside a given JS file, which is going to be a module, you first declare any outside dependencies you want to use, like this:
var React = require('react');
Inside the file/module, you do whatever you normally would, and create some object or function that you'll want to expose to outside users, calling it perhaps myModule.
At the end of a file, you export whatever you want to share with the world, like this:
module.exports = myModule;
Then, to use a CommonJS-based workflow in the browser, you'll use tools like Browserify to grab all those individual module files, encapsulate their contents at runtime, and inject them into each other as needed.
AND, since ES6 modules (which you'll likely transpile to ES5 with Babel or similar) are gaining wide acceptance, and work both in the browser or in Node 4.0, we should mention a good overview of those as well.
More about patterns for working with modules in this deck.
EDIT (Feb 2017): Facebook's Yarn is a very important potential replacement/supplement for npm these days: fast, deterministic, offline package-management that builds on what npm gives you. It's worth a look for any JS project, particularly since it's so easy to swap it in/out.
EDIT (May 2019)
"Bower has finally been deprecated. End of story." (h/t: #DanDascalescu, below, for pithy summary.)
And, while Yarn is still active, a lot of the momentum for it shifted back to npm once it adopted some of Yarn's key features.
2017-Oct update
Bower has finally been deprecated. End of story.
Older answer
From Mattias Petter Johansson, JavaScript developer at Spotify:
In almost all cases, it's more appropriate to use Browserify and npm over Bower. It is simply a better packaging solution for front-end apps than Bower is. At Spotify, we use npm to package entire web modules (html, css, js) and it works very well.
Bower brands itself as the package manager for the web. It would be awesome if this was true - a package manager that made my life better as a front-end developer would be awesome. The problem is that Bower offers no specialized tooling for the purpose. It offers NO tooling that I know of that npm doesn't, and especially none that is specifically useful for front-end developers. There is simply no benefit for a front-end developer to use Bower over npm.
We should stop using bower and consolidate around npm. Thankfully, that is what is happening:
With browserify or webpack, it becomes super-easy to concatenate all your modules into big minified files, which is awesome for performance, especially for mobile devices. Not so with Bower, which will require significantly more labor to get the same effect.
npm also offers you the ability to use multiple versions of modules simultaneously. If you have not done much application development, this might initially strike you as a bad thing, but once you've gone through a few bouts of Dependency hell you will realize that having the ability to have multiple versions of one module is a pretty darn great feature. Note that npm includes a very handy dedupe tool that automatically makes sure that you only use two versions of a module if you actually have to - if two modules both can use the same version of one module, they will. But if they can't, you have a very handy out.
(Note that Webpack and rollup are widely regarded to be better than Browserify as of Aug 2016.)
Bower maintains a single version of modules, it only tries to help you select the correct/best one for you.
Javascript dependency management : npm vs bower vs volo?
NPM is better for node modules because there is a module system and you're working locally.
Bower is good for the browser because currently there is only the global scope, and you want to be very selective about the version you work with.
My team moved away from Bower and migrated to npm because:
Programmatic usage was painful
Bower's interface kept changing
Some features, like the url shorthand, are entirely broken
Using both Bower and npm in the same project is painful
Keeping bower.json version field in sync with git tags is painful
Source control != package management
CommonJS support is not straightforward
For more details, see "Why my team uses npm instead of bower".
Found this useful explanation from http://ng-learn.org/2013/11/Bower-vs-npm/
On one hand npm was created to install modules used in a node.js environment, or development tools built using node.js such Karma, lint, minifiers and so on. npm can install modules locally in a project ( by default in node_modules ) or globally to be used by multiple projects. In large projects the way to specify dependencies is by creating a file called package.json which contains a list of dependencies. That list is recognized by npm when you run npm install, which then downloads and installs them for you.
On the other hand bower was created to manage your frontend dependencies. Libraries like jQuery, AngularJS, underscore, etc. Similar to npm it has a file in which you can specify a list of dependencies called bower.json. In this case your frontend dependencies are installed by running bower install which by default installs them in a folder called bower_components.
As you can see, although they perform a similar task they are targeted to a very different set of libraries.
For many people working with node.js, a major benefit of bower is for managing dependencies that are not javascript at all. If they are working with languages that compile to javascript, npm can be used to manage some of their dependencies. however, not all their dependencies are going to be node.js modules. Some of those that compile to javascript may have weird source language specific mangling that makes passing them around compiled to javascript an inelegant option when users are expecting source code.
Not everything in an npm package needs to be user-facing javascript, but for npm library packages, at least some of it should be.

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