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Using Frontend Libraries

You can build Neutralinojs apps with vanilla JavaScript or with any modern frontend library. If you would like to build Neutralinojs apps with a frontend library, first try to use an existing app template via neu CLI:

React#

neu create myapp --template codezri/neutralinojs-react

Using any frontend library#

The following tutorial guides you to set up any frontend library with Neutralinojs by explaining how we built the Neutralinojs React template:

Initializing projects#

First, you need to create a new empty Neutralinojs project. Use the neutralinojs/neutralinojs-zero template to create an empty project, as shown below.

neu create myapp --template neutralinojs/neutralinojs-zero

Now, create a new project with your favourite frontend framework's command-line tools. In this tutorial, we are going to use React, but you can use any frontend library as you wish. You need to create this project inside the myapp directory.

cd myapp
npx create-react-app react-src

Configuring Neutralinojs project#

The neutralinojs-zero template has a pre-included HTML file and icon, so delete the www directory since we don't need those files now.

rm -rf www

You need to configure the Neutralinojs project to support the frontend framework. First, you can set the document root with your frontend framework's build directory. React typically generates build outputs to build directory, so we can update documentRoot as follows.

"documentRoot": "/react-src/build/"

Now, our Neutralinojs app knows the application resource location, but it's missing an icon, so set an icon for the app. You can load an icon from your frontend framework's default resources directory. For demonstration purposes, let's use the React icon from the public directory.

"modes": {
"window": {
// --- other options
"icon": "/react-src/public/logo192.png"
}
}

Configuring neu CLI#

By default, the zero template configuration asks the Neutralinojs CLI to download the Neutralinojs client (aka neutralino.js) from GitHub releases. Then, the CLI creates your app package by copying the neutralino.js file. However, you can download the client library from the NPM registry and bundle with your app frontend. Remove the clientLibrary property from the Neutralinojs configuration to avoid fetching the client from GitHub releases:

We can configure CLI for React by using the following options.

"cli": {
// --- other options
"resourcesPath": "/react-src/build/",
// ---
"clientLibrary": "/www/neutralino.js", // <--- Remove this option
// ---
}

Now, you can build and run the React application as a Neutralinojs application — it's possible with the following steps.

First, build the React application with the following command.

cd react-src
npm run build

Finally, run the Neutralinojs application.

cd ..
neu run

Initializing native API with @neutralinojs/lib#

You could run the application with the neu run command, but you cannot use the native API yet because it has not been initialized. To do that you need to install the Neutralinojs client with following command:

cd react-src
npm install @neutralinojs/lib

The next step is to load Neutralinojs global variables. You can achieve that by including JavaScript script in the root HTML file of a framework of your choice.

React typically holds the main HTML file content in the ./public/index.html file, so we can put the following HTML snippet there to load the client library.

<script src="%PUBLIC_URL%/__neutralino_globals.js"></script>

Now make sure to initialize the client library from your frontend application entry point file. React's application entry-point is typically ./src/index.js. Therefore, we can do the initialization process from there by calling the init function from @neutralinojs/lib package.

import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
// Import init function from "@neutralinojs/lib"
import { init } from "@neutralinojs/lib"
ReactDOM.render(
<React.StrictMode>
<App />
</React.StrictMode>,
document.getElementById('root')
);
init(); // Add this function call

Let's validate if the client library loaded properly. To do that let's use filesystem API in order to read the current directory of Neutralinojs app.

Firstly you need to update neutralino.config.json to allow what API your application can call. You can enable the whole namespace filesystem.* or just single function from a given namespace like in the snippet below.

"nativeAllowList": [
"app.*",
"filesystem.readDirectory"
],

Now let's add following snippet in ./src/App.js file which will log the current directory or error message when App component is mounted.

import { useEffect } from 'react'
import './App.css';
// Import filesystem namespace
import { filesystem } from "@neutralinojs/lib"
function App() {
// Log current directory or error after component is mounted
useEffect(() => {
filesystem.readDirectory('./').then((data) => {
console.log(data)
}).catch((err) => {
console.log(err)
})
}, [])
return (
<div className="App">
My Neutralinojs App
</div>
);
}
export default App;

The last step is to run your Neutralinojs app with --window-enable-inspector argument which will allow you to open developer tools.

cd react-src
npm run build
cd ..
neu run -- --window-enable-inspector

The current directory should be logged to the console. To open developer tools right click anywhere in the Neutralinojs application and press inspect element.

Enabling hot-reload#

Building every code change and testing your application is undoubtedly time-consuming. Therefore, you can use your frontend framework's HMR (Hot Module Replacement) features to speed up your development activities. But, we have a small issue here. There are now two HTTP servers: the Neutralinojs resource server and the frontend framework's development server. How can we load the Neutralinojs client library from the frontend framework's development server?

Don't worry — neu CLI provides a built-in feature to enable HMR by patching the main HTML file. You can add the following section to your configuration file for activating hot-reloading.

"cli": {
// --- other options
"frontendLibrary": {
"patchFile": "/react-src/public/index.html",
"devUrl": "http://localhost:3000"
}
}
}

The above options tell neu CLI about the main HTML file and development server URL.

Now, start your frontend development server. In React, we can do it with the following command.

npm start

Finally, run the Neutralinojs application with the following command.

neu run --frontend-lib-dev

tip

Make sure to build your frontend app once before entering the above command since it loads the client library globals from the Neutralinojs application resources directory (not from your frontend framework's directory).

Packaging#

To produce the app binaries, first we need to generate static resources via the frontend development tooling. Then, we can generate the Neutralinojs app bundle, as shown in the following command snippet:

cd react-src
npm run build
cd ..
neu build --release

See the full source code of this tutorial here.

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