Building a Desktop App with Vue: NW.js

Previously I've written two articles about building desktop applications with Vue framework: one for Vuido library and one for Electron. I've had some comments requesting an article about NW.js and I promised to write one... and here we go! Better late than never 😅

NW.js (previosly known as node-webkit) is a framework for building desktop applications with HTML, CSS, and JavaScript. It's based on Chromium and Node.js. NW.js lets you call Node.js code and modules directly from browser and also use Web technologies in your app. Further, you can easily package a web application to a native application.

⚛️ Differences from Electron

Electron and NW.js share many features: they are both built on top of Chromium and Node.js and use HTML, CSS and JS for building a desktop app. But they also have some notable differences:

• In NW.js the main entry point of an application is a web page or a JS script. You specify this entry via package.json main property. In Electron, the entry point is a JavaScript script. Instead of providing a URL directly, you manually create a browser window and load an HTML file using the API.
• On build process NW.js builds all Chromium; Electron uses libchromiumcontent to access Chromium's Content API
• NW.js has built-in support for compiling your source code to protected binaries. Electron is packaging its applications with asar, which contains the applications' unprotected source code.

💻 What are we going to build

Now when we understand differences with Electron, we're going to build the same application as in the previous article: an app to check the weather in the city of user's choice built on top of OpenWeatherMap API. This project will be built with Vue CLI and I recommend this way to scaffold any Vue application.

If you want just to check the final NW.js app code, it's here.

🛠️ Installation

Creating an app with Vue CLI

First, let's scaffold an app with Vue CLI. Please make sure you have installed it with typing the following command in your console:

vue --version

If you don't have a version or it's less than 3.x, please run

npm install -g @vue/cli

Now you can create a Vue project from the console! To do so, please run

vue create <<YOUR-PROJECT-NAME>>

and select options you need. I will use the default setup for this project.

Great, now we're ready to add some desktop magic 🧙

Adding NW.js

NW.js official documentation recommends to use one of two builders to package your application:

• nwjs-builder-phoenix
• nw-builder

I chose nwjs-builder-phoenix and I will describe further steps assuming you will use it as well 😅

So, first you need to add it as a dependency to your project:

npm install --save-dev nwjs-builder-phoenix
## OR
yarn add --dev nwjs-builder-phoenix

Now you need to modify your package.json file to provide a correct entry for the packager.

Tip: you can find package.json in the root folder of your application.

Packager entry should be specified under the main property. We're going to run a development environment on the desktop so let's extend our package.json with the following:

"main": "http://localhost:8080"

It's the port where our scaffolded web application is running locally. Usually main is index.html but now we want to have a hot reload on every application change. That's why we're pointing main to a Vue application with hot reload module.

Running an application

Now let's run our web application:

npm run serve
## OR
yarn serve

You can check http://localhost:8080 in your browser to make sure an app is actually running. There should be something like this:

And finally we're ready to start a desktop app:

./node_modules/.bin/run .

This will fetch a specified version of NW.js (by default it's sdk) and run a development environment.

run is a command added by nwjs-builder-phoenix and dot means we're usind the package.json from the root directory.

Now you should have an application running on desktop

Let's automate running dev environment a bit. Close your desktop app and install the NW.js SDK flavor:

npm install --save-dev nw@sdk
## OR
yarn add --dev nw@sdk

Now, add a new task to package.json scripts section:

"scripts": {
  "serve": "vue-cli-service serve",
  "build": "vue-cli-service build",
  "nw-serve": "nw ." /* <--- here is your new npm task */
},

Let's try to run it:

npm run nw-serve
## OR
yarn nw-serve

You should have your app running on desktop again but no downloading step now 🎉

Good news: you can simply open devtools like you do in the browser and use them to debug your application! Just click Window -> Devtools

🕹️ Scaffolding an app

Similarly to Electron, NW.js-powered application is built like a usual web application, so we're going to create a web app, style it with some CSS and let nwjs-builder-phoenix to care about packaging it to desktop application.

NOTE: Same as for Electron app, I didn't install any CSS framework or component library on purpose: I wanted to compare package size without adding any different dependencies. The only library used for all desktop projects is axios.

Open App.vue file and replace its content with the following code:

<template>
  <div id="app">
    <p>Enter the city name to check current weather in it</p>
    <section class="weather-input">
      <input type="text" v-model="query">
      <button :disabled="!query.length">Check</button>
    </section>
  </div>
</template>

<script>
export default {
  data() {
    return {
      query: "",
    };
  }
};
</script>

<style>
#app {
  font-family: "Avenir", Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-align: center;
  color: #2c3e50;
  margin-top: 60px;
}

.button {
  color: #000;
}
</style>

Now our application looks this way:

🔗 Making an API call

I used the OpenWeatherMap current weather API. It gives you a lot of different information, you can check an example of JSON response here.

We're going to use axios to make API calls. Obviously, we need to install it:

npm install axios
## OR
yarn add axios

To be able to use axios inside any Vue component we will import it to main.js, set the base URL and then create a property in Vue prototype for it:

//main.js

import axios from 'axios'

axios.defaults.baseURL = 'http://api.openweathermap.org/data/2.5';
Vue.http = Vue.prototype.$http = axios;

Now in the App.vue we will create a bunch of data properties to display different weather data:

// App.vue

data() {
    return {
      query: '',
      error: false,
      city: '',
      country: '',
      weatherDescription: '',
      temp: null,
      tempMin: null,
      tempMax: null,
      humidity: null,
      icon: '',
    };
},

Similarly to Electron, I've added one additional property comparing to Vuido version and it's an icon. API provides a weather icon but we couldn't use it in Vuido app because currently there is no support for displaying images.

Let's also create a method to fetch our data:

methods: {
  showWeather() {
    this.$http
      .get(`/weather?q=${this.query}&units=metric&&appid=${API_KEY}`)
      .then(response => {
        this.city = response.data.name;
        this.country = response.data.sys.country;
        this.weatherDescription = response.data.weather[0].description;
        this.temp = response.data.main.temp;
        this.tempMin = response.data.main.temp_min;
        this.tempMax = response.data.main.temp_max;
        this.humidity = response.data.main.humidity;
        this.icon = `http://openweathermap.org/img/w/${
          response.data.weather[0].icon
        }.png`;
        this.error = false;
      })
      .catch(() => {
        this.error = true;
        this.city = '';
      });
  },
},

Don't forget to create a const API_KEY with your OpenWeather API key!

and add it to the click callback of our button:

<button :disabled="!query.length" @click="showWeather">Check</button>

Now if you enter the text into an input field and click the button, you can observe the API call in the Network tab:

💅 Displaying weather data

Let's add this data to the template:

<template>
  <main id="app">
    <p>Enter the city name to check current weather in it</p>
    <section class="weather-input">
      <input type="text" v-model="query">
      <button :disabled="!query.length" @click="showWeather">Check</button>
    </section>
    <section v-if="error" class="weather-error">
      There is no such city in the database
    </section>
    <section v-if="city.length" class="weather-result">
      <h1>{{city}}, {{country}}</h1>
      <p><em>{{weatherDescription}}</em></p>
      <div class="weather-result__main">
        <img :src="icon" alt="Weather icon">
        <div class="weather-result__temp">
          {{temp}}&deg;C
        </div>
      </div>
      <div class="weather-result__details">
        <p>Min: {{tempMin}}&deg;C</p>
        <p>Max: {{tempMax}}&deg;C</p>
        <p>Humidity: {{humidity}}%</p>
      </div>
    </section>
  </main>
</template>

Our application view:

It still looks too basic, so it's time to add some CSS. Let's replace the whole style section of App.vue with the following code:

<style>
* {
  margin: 0;
  padding: 0;
}
html,
body,
#app {
  height: 100%;
}

#app {
  font-family: Arial, Helvetica, sans-serif;
  font-size: 16px;
  padding: 10px;
  background: rgb(212, 228, 239);
  background: radial-gradient(
    ellipse at center,
    rgba(212, 228, 239, 1) 0%,
    rgba(134, 174, 204, 1) 100%
  );
  filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#d4e4ef', endColorstr='#86aecc',GradientType=1 ); /* IE6-9 fallback on horizontal gradient */
}

.weather-input {
  display: flex;
  align-items: center;
  padding: 20px 0;
}

.weather-result {
  text-align: center;
}

.weather-result__main {
  display: flex;
  align-items: center;
  justify-content: center;
  padding-top: 5px;
  font-size: 1.3rem;
  font-weight: bold;
}

.weather-result__details {
  display: flex;
  align-items: center;
  justify-content: space-around;
  color: dimgray;
}

.weather-error {
  color: red;
  font-weight: bold;
}

input {
  width: 75%;
  outline: none;
  height: 20px;
  font-size: 0.8rem;
}

button {
  display: block;
  width: 25%;
  height: 25px;
  outline: none;
  border-radius: 5px;
  white-space: nowrap;
  margin: 0 10px;
  font-size: 0.8rem;
}
</style>

And finally we have a beautiful fully-functional app:

The last thing to do before packaging it is to reduce a window size. To do so, we need to add a window property to package.json:

"window": {
  "width": 600,
  "height": 400
},

📦 Packaging

To package a NW.js app with nwjs-builder-phoenix you need to run a build command with a proper set of parameters. I am going to build it on for Mac to compare its size with Electron and Vuido apps.

First, we need to specify a NW.js version to be used on build process. We can do it via build property of package.json

"build": {
  "nwVersion": "0.35.3"
},

And then let's run a build command in the terminal:

./node_modules/.bin/build --tasks mac-x64 .

Again, dot in the command means we're using a package.json file located in the root project folder

Let's check a package size... 233 MB 😱!

Wow, that's a lot. It's even bigger than Electron application!

🌟 Conclusions

Pros:

• really easy to start
• can be customized via CSS styling
• good docs
• has a support for protected binaries

Cons

• very big package size
• not-so-good naming (maybe it's just me but Electron/Vuido is way more memorable than NW.js)
• small ecosystem.

💖 Special thanks

I want to thank Jared Wilcurt who helped me with answers on my NW.js questions. Jared is an author for NW.js Vue devtools to debug a Vue application right on the desktop.

UPDATE: If you wonder how to reduce the size of the package significantly, here is an article by Jared Wilcurt.