I am working on documentation tool for Typescript library. The idea is to leverage parcel's watch mode to continuously build the library, and use the same in a pre-built documentation app.
For the same I need to load a module library (built in another project) dynamically via URL.
<script type="module">
const libraryModule = "http://localhost:8080/lib.module.js";
const promise = import(libraryModule);
promise.then(library => {
// do something with library
window.ComponentLibrary = library;
});
</script>
However, parcel replaces the above import with require and the load fails. Using System.import throws System is not defined error.
I tried to use dynamic-import-polyfill and then initialize it as under and the use as below:
dynamicImportPolyfill.initialize({
modulePath: 'http://localhost:13090', // Defaults to '.'
importFunctionName: '$$import' // Defaults to '__import__'
const promise = $$import(libPath);
});
This throws the following error:
TypeError: Failed to resolve module specifier "react/jsx-dev-runtime". Relative references must start with either "/", "./", or "../"
I have also tried using script type as text/javascript but doesn't work either.
Looking for guidance on the best way here to get the component library loaded?
Figured it out: yes, we can load a component library as a module dynamically.
The issue was that React UMD module is not a pure ES/Javascript module. Also, with React 17, JSX components are picked from react/jsx-runtime. So, first I had to convert the React UMD module into an ES module - it's just a thin wrapper. Similarly, added a wrapper for jsx-runtime. To make things work had to use importmaps which are currently not supported in all browsers - see caniuse.com to check latest support.
This completes your setup and now your library compiled as ES module will work just fine. Below is what I used to get working:
<script type="importmap">
{
"imports": {
"react/jsx-runtime": "/react-jsx-runtime.js",
"react": "/react-as-es-module.js"
}
}
</script>
<script type="module" src="/component-library.js"></script>
<script type="module">
import * as MyComponentLib from "/component-library.js";
window.ComponentLibrary = { ...MyComponentLib };
</script>
Code for react-jsx-runtime.js looks as under:
import * as React from 'react';
export const jsx = React.createElement;
export const jsxs = React.createElement;
Code for react-as-es-module.js goes as:
import 'https://unpkg.com/react#17.0.2/umd/react.production.min.js';
const {
Children,
Component,
Fragment,
// and all other exports
} = React || {};
export {
Children,
Component,
Fragment,
// and all other exports
}
export default React;
I compiled component-library.js using ParcelJS using the type: "module" in package.json file. I would detail this in blog post and demo Github repo soon.
Hope this helps.
Related
i am trying to build web components from react components, it is all working fine, but there are two problems i am trying to solve:
Is there a way to convert such web components to pure web component (using webpack, transpile or some other way), so that react and other dependencies are not bundled?
Is there a way to just include the required portion of dependencies or it is all/none only, and have to use external setting of webpack to use host's version?
thanks
For the first question, there is no direct way to convert React component into a Web Component. You will have to wrap it into a Web Component Class:
export function MyReactComponent() {
return (
<div>
Hello world
</div>
);
}
class MyWebComponent extends HTMLElement {
constructor() {
super();
// Do something more
}
connectedCallback() {
// Create a ShadowDOM
const root = this.attachShadow({ mode: 'open' });
// Create a mount element
const mountPoint = document.createElement('div');
root.appendChild(mountPoint);
// You can directly use shadow root as a mount point
ReactDOM.render(<MyReactComponent />, mountPoint);
}
}
customElements.define('my-web-component', MyWebComponent);
Of course, you can generalize this and create a reusable function as:
function register(MyReactComponent, name) {
const WebComponent = class extends HTMLElement {
constructor() {
super();
// Do something more
}
connectedCallback() {
// Create a ShadowDOM
const root = this.attachShadow({ mode: 'open' });
// Create a mount element
const mountPoint = document.createElement('div');
root.appendChild(mountPoint);
// You can directly use shadow root as a mount point
ReactDOM.render(<MyReactComponent />, mountPoint);
}
}
customElements.define(name, MyWebComponent);
}
register(MyReactComponent, 'my-web-component');
Same register function can be now re-used across all the components that you want to expose as web components. Further, if your component accepts props that should be passed, then this function can be changed to accept third argument as array of string where each value would be registered as a setter for this component using Object.define. Each time a setter is called, you can simply call ReactDOM.render again.
Now for the second question, there are multiple scenarios with what you are trying to do.
If you are bundling application and loading dependencies like React or others using CDN, then Webpack externals is a way to go. Here you will teach Webpack how to replace import or require from the global environment where app will run.
If you are bundling a library which you intend to publish to NPM registry for others to use in their applications, then you must build your project using library target configuration. Read more about authoring libraries here.
Bundling for libraries is slightly trickier as you will have to decide what will be your output format (common.js, ES Modules or UMD or Global or multiple formats). The ideal format is ES Module if you are bundling for browser as it allows better tree shaking. Webpack previously did not support Module format and has recently started supporting it. In general, I recommend Webpack for applications and Rollup.js for libraries.
If you're looking to do this manually, the answer from Harshal Patil is the way to go. I also wanted to point out a library that I helped create, react-to-webcomponent. It simplifies this process and seamlessly supports React 16-18.
React is not a library made to build native web-components.
Writing web-components by hand is not the best option neither as it won't handle conditions, loops, state change, virtual dom and other basic functionalities out of the box.
React, Vue Svelte and other custom libraries certainly have some pros while native web-components have many other advantages like simplicity of ecosystem and being ported by browsers and W3C.
Some libraries that will help you write native web-components in a modern and handy way:
Lego that is alightweight, native and full-featured in a Vue style.
Nativeweb lightweight and raw web-components
ElemX a proof-of-concept that binds native web-component to ElemX functionalities.
If you really wanted to wrap a React component into a native web component, you could do something like:
class MyComponent extends HTMLElement {
constructor() {
this.innerHTML = '<MyReactComponent />'
}
}
customElements.define('my-component', MyComponent)
And use it in your HTML page <my-component />
You can use remount library
/** Main.jsx */
import React from 'react'
import App from './App'
import { define } from 'remount';
define({'react-counter': App},
{
attributes: ['defaultValue'],
shadow:false
})
/** App.jsx */
import React from "react";
import Counter from "./components/Counter.jsx";
function App({defaultValue}) {
return (
<div>
<h1>Counter Component</h1>
<Counter defaultValue={defaultValue}/>
</div>
)
}
export default App;
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<link rel="icon" type="image/svg+xml" href="/vite.svg" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Vite + React</title>
</head>
<body>
<react-counter defaultValue="5"></react-counter>
<script type="module" src="/src/main.jsx"></script>
</body>
</html>
I recently read about React Lazy and how it "loads" the components during run time when they are required to be rendered. I assume that "loading" here means fetching the component from the server and then rendering it.
So my question is, how does React manage this fetching of components? How does it know the exact path from where to fetch this component (given that our code will mention the relative path but fetching will require complete server path)? Does it depend on Webpack for this?
Let's look into the React code. React.lazy is defined as follows.
export function lazy<T, R>(ctor: () => Thenable<T, R>): LazyComponent<T> {
let lazyType = {
$$typeof: REACT_LAZY_TYPE,
_ctor: ctor,
// React uses these fields to store the result.
_status: -1,
_result: null,
};
if (__DEV__) {
// ... additional code only in development mode
}
return lazyType;
}
As you can see, React.lazy requires a Promise which resolves to a module with a default export containing a React component (freely cited by React Docs). This also means that not React resolves the file, but import() does. import() works as documented in the MDN.
The async import() is a new function in ES6 which is not available in all browsers but can be polyfilled by Webpack and Babel/Typescript/others.
What you often see is code like the following, which automatically splits the imported file away by Webpack.
import(/* webpackChunkName: "xyz" */ './component/XYZ')
This creates a new javascript xyz.js next to your bundle script.
If you don't use Webpack, you need to create those files by yourself. Webpack just reduces the work required from you. So you don't absolutely depend on Webpack. This approach might look like the following:
// ./component/xyz.js
export default function() { return <div>Component</div> }
// ./main.js
const OtherComponent = React.lazy(() => import('./component/xyz.js'));
export default function() { return <div>Component</div> }
And the file structure:
| public
|---| main.js
|---| component
|---| --- | main.js
As you see, no webpack required. It just makes your life easier.
I am working on a project that uses "webpack": "^2.4.1",, it is a ReactJS project, I have installed the module airbnb/prop-types-exact, I am using this package for development purposes, where I would not want a user of a component I wrote to pass non-existing properties to that component.
I would like to remove this package when I build the app for production. I am using the Webpack Bundle Initializer to see the bundle size of airbnb/prop-types-exact, it is not that big, but I would like to have it removed from the production build, Is this achievable? With the webpack version that I am using or with a latter one?
I would appreciate any resources or ideas regarding this, thanks.
Following through an example from this Blog by Mark
And more references on these plugins:
IgnorePlugin and DefinePlugin
I have used the plugins as he did, which are IgnorePlugin and UglifyJsPlugin and then in the component where I am using the airbnb/prop-types-exact package, I am doing a check on which environment I am in like..
let exactProps ;
if (process.env.NODE_ENV === "development") {
exactProps = require("prop-types-exact");
}
And depending on whether the exactProps has a value, meaning the require function has ran, and ,meaning the exactProps has the function from the prop-types-exact package,
I am wrapping the my prop types with this function, .eg.
const propTypes = {
someProp: PropTypes.iRequired
}
if (exactProps && typeof exactProps === "function") {
MyComponent.propTypes = exactProps(propTypes);
} else {
MyComponent.propTypes = propTypes;
}
And finally I export the MyComponent component
export MyComponent
I am planning to move the wrapping of the component's prop types into a generic module, so that it is re-usable
I'm building a React application bundled using Parcel or Webpack.
The application should be able to embed external React components
developed by third-parties and hosted elsewhere as modern javascript modules:
// https://example.com/scripts/hello-plugin.js
import React from 'react';
export default class HelloPlugin extends React.Component {
render() {
return "Hello from external plugin!";
}
}
Host application loads these components using asynchronous import like this, for example:
// createAsyncComponent.tsx
import * as React from 'react';
import { asyncComponent } from 'react-async-component';
export default function createAsyncComponent(url: string) {
return asyncComponent({
resolve: () => import(url).then(component => component.default),
LoadingComponent: () => <div>Loading {url}....</div>,
ErrorComponent: ({ error }) => <div>Couldn't load {url}: {error.message}</div>,
})
}
But looks like bundlers don't allow importing arbitrary urls as external javascript modules.
Webpack emits build warnings: "the request of a dependency is an expression" and the import doesn't work. Parcel doesn't report any errors, but fails when import(url) occurs at runtime.
Webpack author recommends using scriptjs or little-loader for loading external scripts.
There is a working sample that loads an UMD component from arbitrary URL like this:
public componentDidMount() {
// expose dependencies as globals
window["React"] = React;
window["PropTypes"] = PropTypes;
// async load of remote UMD component
$script(this.props.url, () => {
const target = window[this.props.name];
if (target) {
this.setState({
Component: target,
error: null,
})
} else {
this.setState({
Component: null,
error: `Cannot load component at ${this.props.url}`,
})
}
});
}
Also, I saw a similar question answered a year ago where the suggested approach also involves passing variables via a window object.
But I'd like to avoid using globals given that most modern browsers support modules out of the box.
I'm wondering if it's possible. Perhaps, any way to instruct the bundler that my import(url) is not a request for the code-split chunk of a host application, but a request for loading an external Javascript module.
In the context of Webpack, you could do something like this:
import(/* webpackIgnore: true */'https://any.url/file.js')
.then((response) => {
response.main({ /* stuff from app plugins need... */ });
});
Then your plugin file would have something like...
const main = (args) => console.log('The plugin was started.');
export { main };
export default main;
Notice you can send stuff from your app's runtime to the plugin at the initialization (i.e. when invoking main at the plugin) of the plugins so you don't end up depending on global variables.
You get caching for free as Webpack remembers (caches) that the given URL has already loaded so subsequent calls to import that URL will resolve immediately.
Note: this seems to work in Chrome, Safari & firefox but not Edge. I never bothered testing in IE or other browsers.
I've tried doing this same sort of load with UMD format on the plugin side and that doesn't seem to work with the way Webpack loads stuff. In fact it's interesting that variables declared as globals, don't end up in the window object of your runtime. You'd have to explicitly do window.aGlobalValue = ... to get something on the global scope.
Obviously you could also use requirejs - or similar - in your app and then just have your plugins follow that API.
Listen to the Webpack author. You can't do (yet) what you're trying to do with Webpack.
You will have to follow his suggested route.
I have a requirejs app and I want to append a react module / component into my page. The react module is written in babel / jsx. So I use the AMD transform plugin AND I concat them into one single file.
Now of course each react js file has export default class / function-part.
One of the react files has a function called startUp(html) which expects a html-element as parameter. This html parameter will be used by ReactDOM.render call.
My problem is that I cannot access the startUp-method in my AMD-module:
////////////////////// REACT AND BABEL / ES6 CODE /////////////////////////
// react-module.js
export default class MyReactContainer extends React.Component {
render() {
return <div>Just a DIV</div>
}
}
// react-main.js
export default function startUp(html) {
ReactDOM.render(<MyReactContainer />, html);
}
//////////////////// EXISTING AMD MODULE /////////////////////////////////
// reactModuleIncluder.js
define(['./react-main'], function(reactMain) {
function includeReactModule(html) {
reactMain(html); // Here I want to call the startUp method
}
return includeReactModule;
});
Any idea what I can do? Or is this even possible?
EDIT: Solved the problem. Files were transpiled and concatenated in one single js file. Now I removed the concat-process and it works.
Solved the problem. Files were transpiled and concatenated in one single js file. Now I removed the concat-process and it works.