We Keep Coding

react code splitting: is the argument for the import() function not a string

This is very bizarre. During my attempt at code-splitting, I encountered this:
const g = "bi";
const importStr = `react-icons/${g.toLowerCase()}`;
console.log(importStr);
console.log(importStr === `react-icons/bi`);
import(importStr).then(module => {
console.log(module);
});
import(`react-icons/bi`).then(module => {
console.log(module);
});
In the above code, if I import "importStr", then the import throws an error:
Uncaught (in promise) Error: Cannot find module 'react-icons/bi'
But if I directly import "react-icons/bi", then there is no issue. As you see,
importStr === `react-icons/bi`
Why and how do I fix this? I can't actually directly use "react-icons/bi" because g is dynamic and could take other values.

I quote from the following comment
Webpack performs a static analyse at build time. It doesn't try to infer variables which that import(test) could be anything, hence the failure. It is also the case for import(path+"a.js").
Because of the tree shaking feature webpack tries to remove all unused code from the bundle. That also means something similar could work
import("react-icons/" + g)
Edit: as per your suggestion I updating this to
import("react-icons/" + g.toLowerCase()+ '/index.js')

An easy way to implement code splitting in React is with lazy loading, as seen here (this might be easier than importing a dynamic string):
const OtherComponent = React.lazy(() => import('./OtherComponent'));
This implementation will load the bundle with OtherComponent only when it is first rendered.
Example from reactjs.org:
import React, { Suspense } from 'react';
const OtherComponent = React.lazy(() => import('./OtherComponent'));
const AnotherComponent = React.lazy(() => import('./AnotherComponent'));
function MyComponent() {
return (
<div>
<Suspense fallback={<div>Loading...</div>}>
<section>
<OtherComponent />
<AnotherComponent />
</section>
</Suspense>
</div>
);
}
More info on React.lazy

import npm modules asynchronously in react.js

I am using parcel as a bundler in React.js project.
How to load npm modules asynchronously in react.js?
There is only one page that uses one specific npm module so I didn't need to load it at first loading.
By avoiding this, I would like to reduce the bundle size.
Could you let me the proper way to do this?
========================
And also, if I understood anything wrongly about the bundle size optimization and lazy loading, please let me know.

By using Dynamic Import you may import the package when you really need the package.

You can use a dynamic import inside an useEffect hook like:
const Page = (props) => {
useEffect(
() => {
const [momentjsPromise, cancel] = makeCancelable(import("moment"));
momentjsPromise.then((momentjs) => {
// handle states here
});
return () => {
cancel?.();
};
},
[
/* don't forget the dependencies */
],
);
};

You can use dynamic imports.
Let's say you want to import my-module:
const Component = () => {
useEffect(() => {
import('my-module').then(mod => {
// my-module is ready
console.log(mod);
});
}, []);
return <div>my app</div>
}
Another way is to code-splitt Component itself:
// ./Component.js
import myModule from 'my-module';
export default () => <div>my app</div>
// ./App.js
const OtherComponent = React.lazy(() => import('./Component'));
const App = () => (
<Suspense>
<OtherComponent />
<Suspense>
);
my-module will be splitted along with Component.
These two patterns should work with any bundler, but it will work client side only.

Internationalization gone wrong in gatsby

ERROR #95313 Building static HTML failed for path "/404/"
I recently implemented localization in my gatsby project using the react-intl package. I was able to pull that off by mimicking the implementation of the package in the gatsby-starter-default-contentful-i18n repo. Everything works fine when I run gatsby-develop but sadly not the same after running build.
The react-intl packages require some route configurations to get it up and running, which made me make use of the location props in my layout component which is exposed to the route paths which I also implemented using the earlier linked repo as a guide. However, I always meet this error.
const url = location.pathname;
| ^
36 | const { langs, defaultLangKey } = data.site.siteMetadata.languages;
37 | const langKey = getCurrentLangKey(langs, defaultLangKey, url);
38 | const homeLink = `/${langKey}/`;
-WebpackError: TypeError: Cannot read property 'pathname' of undefined.
I keep getting pointed towards the url variable. I made sure to cross-check all the location props that were passed down from layout component parents to make sure none of them were undefined, but still no dice. I really don't know where to start debugging this problem.
Below is my index.js file.
import React from 'react';
import { graphql, navigate, withPrefix } from 'gatsby';
import { getUserLangKey } from 'ptz-i18n';
class RedirectIndex extends React.PureComponent {
constructor(args) {
super(args);
// Skip build, Browsers only
if (typeof window !== 'undefined') {
const { langs, defaultLangKey } = args.data.site.siteMetadata.languages;
const langKey = getUserLangKey(langs, defaultLangKey);
const homeUrl = withPrefix(`/${langKey}/`);
navigate(homeUrl);
}
}
render() {
// It's recommended to add your SEO solution in here for bots
// eg. https://github.com/ahimsayogajp/ahimsayoga-gatsby/blob/master/src/pages/index.js#L22
return (<div />);
}
}
export default RedirectIndex;
export const pageQuery = graphql`
query IndexQuery {
site{
siteMetadata{
languages {
defaultLangKey
langs
}
}
}
}
`;
Thanks in advance for all the help!

How can I dynamically export components in index.js?

I'm working on a project with nuxt.js and I want to implement the atomic design methodology
so I currently import the components like this
import ButtonStyled from '#/components/atoms/ButtonStyled.vue'
import TextLead from '#/components/atoms/TextLead.vue'
import InputSearch from '#/components/atoms/InputSearch.vue'
but I need to import like this
import {
ButtonStyled,
TextLead,
InputSearch
} from '#/components/atoms'
the closer I got was that,
/atoms/index.js
const req = require.context('./', true, /\.vue$/)
const modules = {}
req.keys().forEach(fileName => {
const componentName = fileName.replace(/^.+\/([^/]+)\.vue/, '$1')
modules[componentName] = req(fileName).default
})
export const { ButtonStyled, TextLead } = modules
but I'm still defining the export variable names statically, I need to define dynamics based on the components inside the folder
NOTE: I can not use
export default modules
if I use the above code snippet I will not be able to import the way I need it, which is:
import { ButtonStyled } from "#/components/atoms"

require.context is a quite obscure function in Webpack, you will have issues while running unit tests. But, to solve your problem; You will need to import the index.js file in the main.js of your project.
This is how I do it:
_globals.js
// Globally register all base components prefixed with _base for convenience, because they
// will be used very frequently. Components are registered using the
// PascalCased version of their file name.
import Vue from 'vue'
import upperFirst from 'lodash/upperFirst'
import camelCase from 'lodash/camelCase'
const requireComponent = require.context('.', true, /_base-[\w-]+\.vue$/)
requireComponent.keys().forEach(fileName => {
const componentConfig = requireComponent(fileName)
const componentName = upperFirst(
camelCase(fileName.replace(/^\.\/_base/, '').replace(/\.\w+$/, ''))
)
Vue.component(componentName, componentConfig.default || componentConfig)
})
components/index.js
//...
import './_globals'
//...
main.js
//...
import './components' // This imports in the index.js
//...
This way your components loaded in with require.context() gets registered as a vue component and made globally available. I advice to only use global components with components that will be used a lot. Do not load a component globally if you intend to use it only one time.
You can find a working example here -> https://github.com/IlyasDeckers/vuetiful/tree/master/src
To get your unit tests working with jest, you will need to mock require.context(). This was a true pain, but can be achieved easily by using babel-plugin-transform-require-context

I try to use your way to do that, and known you have make a mistake at module.exports
module.exports can not use import , i think you may can do like this
at atoms/index.js
const req = require.context("./", true, /\.vue$/);
const atoms = {};
req.keys().forEach(fileName => {
const componentName = fileName.replace(/^.+\/([^/]+)\.vue/, "$1");
atoms[componentName] = req(fileName).default;
});
export default atoms;
at where to use
import k from "#/components/atoms/index.js";
export default {
components: {
test1: k.test1,
test2: k.test2
}
};
or index.js
import test1 from "./test1.vue";
import test2 from "./test2.vue";
export { test1, test2 };
and where to use like this
import {test1,test2} from "#/components/atoms/index.js";
export default {
components: {
test1,
test2
}
};

I created a library that does all this for me, maybe it helps other people.
named-exports

Passing component as a function argument

I have a function that take a component as argument, and return another, enhanced component:
import React from 'react';
import { compose } from 'recompose';
import { connect } from 'react-redux';
import { Link } from 'react-router-dom';
import { Layout, DarkBar } from 'SharedComponents/Layouts';
const myCreationFunction = ({
component,
}) => {
const Route = (props) => {
// Some code here
return (
<Layout>
<div><Link to={props.path}>LinkTitleHere</Link></div>
{React.createElement(component, {
...props,
...someOtherPropsHere,
})}
</Layout>
);
}; // The error points here
const mapStateToProps = () => ({});
const enhance = compose(
connect(mapStateToProps, someActionsHere),
)(Route);
return enhance;
};
I invoke that function in this way:
import MyComponent from './MyComponent';
import myCreationFunction from './HOC/myCreationFunction';
const Route = myCreationFunction({
component: MyComponent,
});
When I run it in the development mode, it runs smoothly. But when trying to build the app using npm run build and going through webpack, I get:
Module parse failed: Unexpected token (35:47)
You may need an appropriate loader to handle this file type.
| function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
|
> var createListRoute = function myCreationFunction((_temp = _ref, _ref2 = <_Layouts.DarkBar>
| <_Breadcrumbs2.default />
| <_Layouts.RoundAddButton path={addPath} color="white" />
What am I doing wrong?
Edit #1
It seems that the <Link> is causing the problem. Removing it fixed the problem. Also, when trying to replace it with a tag, I get the same issue. Weird.
Edit #2
I have not resolved this issue because of lack of time. I was trying for 1 hour without any progress and decided to go with button tag and onClick method that uses history to push the new url.
It was and is really weird to me, that a Link or <a> tag can break something during the build process itself. I will definitely jump deeper into it in some free time.