kotatsu is a straightforward CLI tool aiming either at running node.js scripts or serving JavaScript web applications in a modern environment (modules, ES2015, Hot Module Replacement, etc.).
Its goal is to relieve developers from the really heavy stack that we now face on a daily basis when working with modern JavaScript.
The idea is to let developers new to the stack forget about it as long as they can while enabling seasoned developers to setup their environment very fast and to start customizing the stack progressively only when this is really needed.
Typical use cases for kotatsu are hot-reloaded express APIs written in ES2015, hot-reloaded React or deku applications etc. Check the use cases for a quick glance of what can be achieved.
Note that kotatsu currently uses webpack under the hood to perform its magic.
Kotatsu can be installed globally (you should avoid this!) or within your node.js project using npm:
# Within your project
npm install --save-dev kotatsu
# Globally:
[sudo] npm install -g kotatsuNote that kotatsu has been designed to work with npm v3 rather than npm v2. So, while it can work with older version of node & npm, it is recommended that you use node v5 and npm v3 when using the this tool.
If you wonder how to install & switch node versions comfortably, you should probably check out nvm.
Usage: kotatsu <command> {options} [entry]
Commands:
start Start a node.js script.
serve Serve a client-side application.
---
monitor Monitor a terminating node.js script.
run Run the given node.js script.
build Build your code for client or server.
Options:
-c, --config Optional webpack config that will be merged with kotatsu's one (useful if you
need specific loaders).
-d, --devtool Webpack devtool spec to use to compute source maps. [string]
-m, --mount-node Id of the mount node in the generated HMTL index. [string]
-o, --output Output path (either directory or filename). [string]
-p, --port Port that the server should listen to. [default: 3000]
-s, --source-maps Should source maps be computed for easier debugging? [boolean] [default: true]
--babel Use Babel to compile the files. [boolean] [default: false]
--cors Should the server allow CORS? [boolean] [default: true]
--es2015 Is your code written in ES2015? [boolean] [default: false]
--index Path to a custom HMTL index file. [string]
--jsx Does your code uses JSX syntax? [boolean] [default: false]
--minify Minify the bundle. [boolean] [default: false]
--pragma JSX pragma. [string]
--presets Babel 6 presets separated by a comma (example: es2015,react). [string]
--progress Should it display the compilation's progress? [boolean] [default: false]
--proxy Proxy information (example: /api http://localhost:4000) [string]
--public Path to a public folder (can be used multiple times). [string]
--quiet Disable logs. [boolean] [default: false]
--version Show version number [boolean]
-h, --help Show help [boolean]
Examples:
kotatsu start script.js Launching the given script with HMR.
kotatsu start --es2015 scripts.js Launching a ES2015 script.
kotatsu start -c webpack.config.js script.js Using a specific webpack config.
kotatsu start --no-source-maps script.js Disabling source maps.
kotatsu start script.js -- --path test.js Passing arguments to the script.
kotatsu serve entry.js Serving the given app.
kotatsu serve --es2015 --jsx entry.jsx Serving the given ES2015 & JSX app.
kotatsu serve --port 8000 entry.jsx Serving the app on a different port.
kotatsu serve --babel entry.js Enable Babel to use .babelrc files.
kotatsu serve --proxy /api http://localhost:4000 Proxying an API.
kotatsu build server --es2015 entry.js -o ./ Build the given script.
kotatsu build client entry.js -o build Build the given client app.
If this is your first time using kotatsu, you should really check the use cases below to see how it could fit your workflow.
This example does not really serve a real-life purpose but merely shows you how to hot-reload a very simple node.js script.
The idea here is to create a script that will continuously print a required string into the console every 2 seconds:
1. Creating the necessary files
// file: interval.js
var string = require('./string.js');
setInterval(function() {
console.log(string);
}, 2000);
// Here is the twist: whenever the `string` dependency is updated, we will swap it:
if (module.hot) {
module.hot.accept('./string.js', function() {
string = require('./string.js');
});
}// file: string.js
module.exports = 'ping';2. Using kotatsu to start the script
kotatsu start interval.jsNow the script will start and you should see it logging ping into the console every two seconds.
Now edit the string.js file and the script will automatically update and log the new exported value of the file.
3. Let's use the same script in the browser
You would rather run this script in the browser?
kotatsu serve interval.jsNow go to localhost:3000 and you should be able to observe the same kind of results in the console.
Remarks
This example serves another purposes: showing you that kotatsu is meant to be used on long-running scripts such as servers or UIs. If what you need is to code a terminating script, check the monitor command instead.
If you need more information about module.hot and Hot Module Replacement (HMR), go check webpack's docs on the subject.
Let's setup a very simple hot-reloaded express app:
1. Installing necessary dependencies
npm i --save express
npm i --save-dev kotatsu2. Creating our app
// file: app.js
var express = require('express');
var app = express();
app.get('/', function(req, res) {
return res.send('Hello World!');
});3. Creating our startup script
// file: start.js
var app = require('./app.js'),
http = require('http');
var server = http.createServer(app);
server.listen(3000);
if (module.hot) {
// This will handle HMR and reload the server
module.hot.accept('./app.js', function() {
server.removeListener('request', app);
app = require('./app.js');
server.on('request', app);
console.log('Server reloaded!');
});
}4. Using kotatsu
Launching our app with HMR so we can work comfortably.
kotatsu start ./start.jsYou can now edit the express app live and it will automatically update without having to reload the script.
1. Installing necessary dependencies
npm i --save deku
npm i --save-dev kotatsu2. Creating our main component
// file: App.jsx
import {element} from 'deku';
export default function App() {
return <div>Hello World!</div>;
}3. Creating our application's entry
// file: main.jsx
import {dom, element} from 'deku';
import InitalApp from './App.jsx';
const mountNode = document.getElementById('app'),
render = dom.createRenderer(mountNode);
function refresh(Component) {
render(<Component />);
}
refresh(InitalApp);
// Let's handle our code's updates
if (module.hot) {
module.hot.accept('./App.jsx', function() {
const NextApp = require('./App.jsx');
refresh(NextApp);
});
}4. Using kotatsu
Now let's run a server to host our app:
kotatsu serve --es2015 --jsx --pragma element main.jsxNote that kotatsu will serve for you a HTML index file looking quite like this:
<!DOCTYPE html>
<html>
<head>
<title>kotatsu</title>
</head>
<body>
<div id="app"></div>
<script type="text/javascript" src="/build/bundle.js"></script>
</body>
</html>If you need a custom one, just use the --index argument.
Now visit localhost:3000 and you are ready to develop.
React is a bit more tricky because we need to install a Babel 6 preset (react-hmre) to handle hot-loading.
1. Installing necessary dependencies
npm i --save react react-dom
npm i --save-dev kotatsu babel-preset-react babel-preset-react-hmre2. Creating our main component
// file: App.jsx
import React, {Component} from 'react';
export default class App extends Component {
render() {
return <div>Hello World!</div>;
}
}3. Creating our application's entry
// file: main.jsx
import React from 'react';
import {render} from 'react-dom';
import App from './App.jsx';
const mountNode = document.getElementById('app');
render(<App />);4. Using kotatsu
Now let's run a server to host our app:
kotatsu serve --presets es2015,react,react-hmre ./main.jsxNote that kotatsu will serve for you a HTML index file looking quite like this:
<!DOCTYPE html>
<html>
<head>
<title>kotatsu</title>
</head>
<body>
<div id="app"></div>
<script type="text/javascript" src="/build/bundle.js"></script>
</body>
</html>If you need a custom one, just use the --index argument.
Now visit localhost:3000 and you are ready to develop.
var kotatsu = require('kotatsu');Every method of the library uses the same configuration object (similar to the CLI arguments):
required
- entry string: Path towards the entry.
optional
- args array: array of arguments to pass to the child script.
- cwd string [
process.cwd()]: current working directory. - config object: a webpack config object.
- cors boolean [
true]: should the server allow CORS? - devtool string: a webpack devtool spec.
- es2015 boolean [
false]: should we handle ES2015 files? - index string: path of the HTML index file to serve.
- jsx boolean [
false]: should we handle JSX? - minify boolean [
false]: should the bundle be minified. - mountNode string [
'app']: id of the mount node in the generated HTML index file. - output string [
.kotatsu]: path of the built file. - port integer [
3000]: port that the server should listen to. - pragma string: custom JSX pragma.
- presets array: Babel 6 presets to apply.
- progress boolean [
false]: should the compiler display a progress bar? - proxy array: proxy information.
- quiet boolean [
false]: if true, will disable all console logs. - server function: function called with the express app in case you want to apply custom middlewares etc.
- sourceMaps boolean [
true]: should it compute source maps?
var watcher = kotatsu.start({
entry: 'script.js',
...
})var server = kotatsu.serve({
entry: 'script.js',
...
})var watcher = kotatsu.monitor({
entry: 'script.js',
...
})kotatsu.run({
entry: 'script.js',
...
});// side can be either 'front' or 'back'
kotatsu.build(side, {
entry: 'script.js',
...
});A kotatsu is a low Japanase table covered by a heavy blanket with an underneath heat source that keeps you warm in the cold season.
kotatsu is widely inspired by the following modules:
- webpack-hot-middleware by @glenjamin.
- nodemon by @remy.
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