I'm using create-react-app. When I run npm start (react-scripts start) it continuously builds the changes for me and does it magic. But what is the output folder for that? I know when I build it manually where the files go.
I want to use firebase emulator to serve the current version (the continuous build) of my react all but I don't understand where's the output folder or how to achieve it.
You could try this package https://github.com/Nargonath/cra-build-watch
Install it and add the script to your package.json
{
"scripts": {
"watch": "cra-build-watch"
}
}
and run it
npm run watch
more info here
https://ibraheem.ca/writings/cra-write-to-disk-in-dev/
and if you go to the react repo issue linked in the article you would find more workarounds
tl;dr
run npm run build, not npm run start
More Detail
react-scripts start runs webpack-dev-server internally. As a default setting, webpack-dev-server serves bundled files from memory and does not write files in directory.
If you want to write files with webpack-dev-sever, you could set writeToDisk option to true in your dev server configuration.
However, I dont think this is what you want to serve on firebase emulator. Webpack-dev-server does not build optimal app for production, and you also need to use react-app-rewired to customize dev server configuration in cra template.
What you want to do is npm run build to run react-scripts build, which builds optimized production app in /build directory.
There is some license issue with one of the dependencies getting installed with react-scripts.
Project is created using CRA, so react-scripts is marked as dependency in package.json.
If I mark react-scripts as dev-dependency, since i don't need it for production, and install all the packages using 'npm install --production', I will not be able to use build script as react-scripts is not installed.
Browsing around this I see react-scripts should ideally be a Dev-dependency.
So just wanted to check if anyone can help here, how to use build script keeping react-scripts as Dev-dependency? is using webpack as a to bundle would be the only option here?
NPM and package.json initially were created for Node.js, which is intended to either run some scripts, or to run continuously. In this cases you might need some dependencies only when you are developing (for example some debuggers, or nodemon and so on), but don't need them in production.
In case of CRA, you don't need any dependencies on production, since you are building bunch of static files. Generally, you have some build pipeline, that will install all dependencies, build your static files and then transfer only built files to produciton (where only production dependencies may be installed again, or it can be another build step in pipeline). If you don't have such pipeline, you can install all dependencies, build on server and then delete node_modules.
I am building a react project which has 2 separate Jest configs for my frontend and backend tests. My frontend tests use React Testing Library which requires the "jsdom" test environment and my backend tests use mongoose which requires the "node" test environment. I am trying to use the jest "projects" config in my package.json in order to run the two testing suites simultaneously with their respective environments like so:
{
"jest": {
"projects": [
"backend/config/jest.config.js",
"src/jest.config.js"
]
}
}
However, when I try to run the tests, I get this message:
Out of the box, Create React App only supports overriding these Jest options:
• clearMocks
• collectCoverageFrom
• coveragePathIgnorePatterns
• coverageReporters
• coverageThreshold
• displayName
• extraGlobals
• globalSetup
• globalTeardown
• moduleNameMapper
• resetMocks
• resetModules
• restoreMocks
• snapshotSerializers
• transform
• transformIgnorePatterns
• watchPathIgnorePatterns.
These options in your package.json Jest configuration are not currently supported by Create React App:
• projects
If you wish to override other Jest options, you need to eject from the default setup. You can do so by running npm run eject but remember that this is a one-way operation. You may also file an issue with Create React App to discuss supporting more options out of the box.
I'm not quite sure what do to here. Any way to make the jest "projects" option work the create-react-app?
I am trying to integrate Jest flow runner with my app created with create-react-app as I want to run my flow type checks along with the test cases.
I followed the steps given in the Jest platforms video and added:-
{
"jest": {
"runner": "jest-runner-flowtype"
}
}
in my package.json but got this message:-
Out of the box, Create React App only supports overriding these Jest
options:
• collectCoverageFrom
• coverageReporters
• coverageThreshold
• snapshotSerializers.
These options in your package.json Jest configuration are not currently supported by Create React App:
• runner
If you wish to override other Jest options, you need to eject from the default setup. You can do so by running npm run eject but remember that this is a one-way operation. You may also file an issue with Create React App to discuss supporting more options out of the box.
Is there a way to use both jest flow runner & test runner at the same time with jest?
I read on create-react-app testing guide but couldn't find a way to add one runner.
Update:
I tried ejecting from the create-react-app and added projects option:-
"projects": [
{
"displayName": "flow",
"runner": "jest-runner-flowtype",
"testMatch": ["<rootDir>/**/*.js"]
}
]
and tried running yarn jest --env=jsdom still no flow types are errors are being displayed.
I've been working with a React project using create-react-app and I have two options to start the project:
First way:
npm run start with the definition at the package.json like this:
"start": "react-scripts start",
Second way:
npm start
What is the difference between these two commands? And, what is the purpose of the react-scripts start?
I tried to find the definition, but I just found a package with this name. I still don't know what is the use of this command?
create-react-app and react-scripts
react-scripts is a set of scripts from the create-react-app starter pack. create-react-app helps you kick off projects without configuring, so you do not have to setup your project by yourself.
react-scripts start sets up the development environment and starts a server, as well as hot module reloading. You can read here to see what everything it does for you.
with create-react-app you have following features out of the box.
React, JSX, ES6, and Flow syntax support.
Language extras beyond ES6 like the object spread operator.
Autoprefixed CSS, so you don’t need -webkit- or other prefixes.
A fast interactive unit test runner with built-in support for coverage reporting.
A live development server that warns about common mistakes.
A build script to bundle JS, CSS, and images for production, with hashes and sourcemaps.
An offline-first service worker and a web app manifest, meeting all the Progressive Web App criteria.
Hassle-free updates for the above tools with a single dependency.
npm scripts
npm start is a shortcut for npm run start.
npm run is used to run scripts that you define in the scripts object of your package.json
if there is no start key in the scripts object, it will default to node server.js
Sometimes you want to do more than the react scripts gives you, in this case you can do react-scripts eject. This will transform your project from a "managed" state into a not managed state, where you have full control over dependencies, build scripts and other configurations.
As Sagiv b.g. pointed out, the npm start command is a shortcut for npm run start. I just wanted to add a real-life example to clarify it a bit more.
The setup below comes from the create-react-app github repo. The package.json defines a bunch of scripts which define the actual flow.
"scripts": {
"start": "npm-run-all -p watch-css start-js",
"build": "npm run build-css && react-scripts build",
"watch-css": "npm run build-css && node-sass-chokidar --include-path ./src --include-path ./node_modules src/ -o src/ --watch --recursive",
"build-css": "node-sass-chokidar --include-path ./src --include-path ./node_modules src/ -o src/",
"start-js": "react-scripts start"
},
For clarity, I added a diagram.
The blue boxes are references to scripts, all of which you could executed directly with an npm run <script-name> command. But as you can see, actually there are only 2 practical flows:
npm run start
npm run build
The grey boxes are commands which can be executed from the command line.
So, for instance, if you run npm start (or npm run start) that actually translate to the npm-run-all -p watch-css start-js command, which is executed from the commandline.
In my case, I have this special npm-run-all command, which is a popular plugin that searches for scripts that start with "build:", and executes all of those. I actually don't have any that match that pattern. But it can also be used to run multiple commands in parallel, which it does here, using the -p <command1> <command2> switch. So, here it executes 2 scripts, i.e. watch-css and start-js. (Those last mentioned scripts are watchers which monitor file changes, and will only finish when killed.)
The watch-css makes sure that the *.scss files are translated to *.cssfiles, and looks for future updates.
The start-js points to the react-scripts start which hosts the website in a development mode.
In conclusion, the npm start command is configurable. If you want to know what it does, then you have to check the package.json file. (and you may want to make a little diagram when things get complicated).
succinctly - it runs this
node node_modules/react-scripts/bin/react-scripts.js start
"start" is a name of a script, in npm you run scripts like this npm run scriptName, npm start is also a short for npm run start
As for "react-scripts" this is a script related specifically to create-react-app
npm start is the short form for npm run start
You can check about it here Difference between npm start and npm run start
react-scripts start
react-scripts is a set of scripts to support the creation, development and testing of react applications. It is used by create-react-app.
create-react-app is the officially supported way to create single-page React applications. create react app uses webpack to parse and bundle the application.
webpack parses the application and creates a dependency graph from its entry point specified in the webpack config file. while parsing, webpack uses babel to transpile the application to JavaScript, which has better support across browsers.
Webpack uses the generated dependency graph to create a single JavaScript file consisting of the application source code and modules used by the app, injects the file via script tag into public/index.html, and starts a development server on http://localhost:3000. Navigating to this URL in the browser will show a live, interactive instance of your application. Any changes saved to the source code will reflect in the running app instance automatically.
You can read more about this topic more on here