To elaborate:
Lets say I have a react native project running on a specific version, and there are different npm packages installed, We know that each npm package will have its own node_modules and build.gradle file, In what scenario those dependencies local to that package will be used in my project and in what scenarios my project's dependencies will be used?
In the react native new architecture turbo modules are supported whereas I am using a library that does not has turbo modules enable is working, just wanted to know on what grounds the local versions of that package is being used and not the ones present in my project
Let's say for example that you are using react-native-reanimated 2. This package has react-native-gesture-handler as its dependency. In most cases you'll have react-native-gesture-handler added as a local dependency as well.
Now, wherever you are importing reanimated 2 and using its functions, the react-native-gesture-handler of reanimated will be used, not your local one. In some cases, a conflict arises where different versions of dependencies make conflict. In that case you can use resolutions or override in package.json
In your specific case, if a library you are using does not support turbo modules then it will not work with new architecture because new architecture only supports turbo modules as native module.
We're using Material UI in our project, but there're many components that's shared between a few projects, se I'm creating a React components library to share them.
But when I import the component from library, I got the warning about #material-ui/styles:
It looks like there are several instances of `#material-ui/styles` initialized in this application.
This may cause theme propagation issues, broken class names, specificity issues, and makes your application bigger without a good reason.
I've checked by npm ls #material-ui/styles that there're only a single version.
But this problem is still happening even I added #material-ui/core, #material-ui/styles to the peerDependencies.
How can I fix this?
From the Materal UI docs:
Possible reasons
There are several common reasons for this to happen:
You have another #material-ui/styles library somewhere in your dependencies.
You have a monorepo structure for your project (e.g, lerna, yarn workspaces) and #material-ui/styles module is a dependency in more than one package (this one is more or less the same as the previous one).
You have several applications that are using #material-ui/styles running on the same page (e.g., several entry points in webpack are loaded on the same page).
As said by #Code-Apprentice one or more libraries are using #material-ui/styles (I bet it's react bootstrap). It doesn't really seem to be harmful but one way of fixing it is removing dependencies that use the #material-ui/styles.
I have a React-webpack web app (client side only - no API server) and was tidying up the package.json file and it occurred to me that all of the dependencies are dev dependencies as you do not run the React web app in production - you build it and distribute the built files.
Is this right?
React and possibly ReactDOM would be dependencies. Any additional libraries you're using that appear on the page would also be dependencies (example: react-autosuggest). Everything else would generally be a devDependency.
There's no great consensus on this yet (see this webpack issue, for instance). Some folks want to do everything as a dependency, others as a devDependency, I'm sure you could make a case for bundled dependencies, etc. The solution I outlined above is a best practice that seems to work well. For example, if you're using a version range on a package, you likely wouldn't care about minor/patch version change to webpack, eslint, karma, mocha, etc. You'd most certainly care about even a patch level change to something like react, so it gets separated out into a much shorter dependency list. (Looking at one project, there seems to be a 4-5x difference between dependency and devDependency. It's much easier to spot the meaningful changes if you corral them into the dependency tree.)
Related: yarn takes the approach I outlined above.
I want to have a project structure like that:
./app/package.json
./app/src/index.js
./widget1/package.json
./widget1/src/index.js
./widget2/package.json
./widget2/src/index.js
./widget3/package.json
./widget3/src/index.js
As you can guess, this project is like an aggregation of NPM widget subprojects, and the app src folder is the real app, that uses the different widget subprojects.
I want a clear and strict separation between the widgets because my current experience shows me that developers tend to introduce unwanted cyclic dependencies between widgets even if I tell them not too.
In practice, all these widgets will be ReactJS widgets that have for most of them 3 common JS libs: React, JQuery and Lodash. Some will not need these 3 libs, some will need an additional lib like packery, react-slick or react-date-picker All these widgets should also share common test libraries like mocha.
They absolutly need to share the exact same common library versions (because obviously I don't want different versions of React in my project nor to increase my bundle size).
For example,
- widget1 could be a DatePicker widget, that depends on React + Lodash + react-date-picker (npm lib, not mine)
- The app project could depend on React + Redux + Normalizr + all the widgets and their transitive dependencies like react-date-picker
All the widgets will be Presentational components and do not need much more fancy dependencies. Some will only depend on React. Some may have a Redux reducer but as it is plain old JS code, there's no dependency needed.
The number of widgets can be quite big and I don't want to edit 200 package.json files on each library update (however I could eventually use some code to handle that).
When inside widget1/src, it should be forbidden to require code from widget2. If a widget had to be able to depend on another widget, this dependency must be set explicitly in package.json of the client widget.
I should be able to build with Webpack and test all the widgets independently. I should also be able to build and test at once the whole project, including all the subprojects, and having a single aggregated global test and code coverage report.
I don't want it to have a bad developer experience. React and Webpack permits to have Hot code reloading. If I have the real app in my browser and I modify code of a widget, I should be able to see the change live with react-hot-loader and not have to run npm commands nor hit F5.
What I look for is the equivalent of Java Maven's dependencyManagement system where you usually set versions for all your subprojects in parent POM, and versions are somehow inherited to all child projects. All child projects cannot see each others (unless explicit dependency is added), but they can say they depend on a library declared in parent project. All the lib version numbers can be set in the parent project.
Is it possible to do so with NPM and Webpack?
Or at least something close to it?
Thanks
You could put each widget in it's own git repo and install them with NPM via the repo URL. As long as each widget defines the libraries they use in their own NPM package, when they're used in the main project NPM will handle all of the dependencies for you.
Depending on the size of your team you could also sign up for NPM's private packages and host them there https://www.npmjs.com/npm/private-packages
You might want to try https://github.com/n8tz/layer-pack,
as it meets many of the needs mentioned
It allows to:
inherit several npm packages in 1 source tree
manage module inheritance ( drive node & webpack to resolve them well )
put all Webpack conf & profiles in a shared, inheritable and versioned package
etc...
Note that hot reloading with too many inherited packages can be slow.
Alternative is to use precompiled versions of your widgets & externalize theirs deps.
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.