Adding React based World Mood Tracker to loklak Apps

loklak apps is a website that hosts various apps that are built by using loklak API. It uses static pages and angular.js to make API calls and show results from users. As a part of my GSoC project, I had to introduce the World Mood Tracker app using loklak’s mood API. But since I had planned to work on React, I had to go off from the track of typical app development in loklak apps and integrate a React app in apps.loklak.org.

In this blog post, I will be discussing how I introduced a React based app to apps.loklak.org and solved the problem of country-wise visualisation of mood related data on a World map.

Setting up development environment inside apps.loklak.org

After following the steps to create a new app in apps.loklak.org, I needed to add proper tools and libraries for smooth development of the World Mood Tracker app. In this section, I’ll be explaining the basic configuration that made it possible for a React app to be functional in the angular environment.

Pre-requisites

The most obvious prerequisite for the project was Node.js. I used node v8.0.0 while development of the app. Instead of npm, I decided to go with yarn because of offline caching and Internet speed issues in India.

Webpack and Babel

To begin with, I initiated yarn in the app directory inside project and added basic dependencies –

$ yarn init
$ yarn add webpack webpack-dev-server path
$ yarn add babel-loader babel-core babel-preset-es2015 babel-preset-react --dev

 

Next, I configured webpack to set an entry point and output path for the node project in webpack.config.js

module.exports = {
    entry: './js/index.js',
    output: {
        path: path.resolve('.'),
        filename: 'index_bundle.js'
    },
    ...
};

This would signal to look for ./js/index.js as an entry point while bundling. Similarly, I configured babel for es2015 and React presets –

{
  "presets":[
    "es2015", "react"
  ]
}

 

After this, I was in a state to define loaders for module in webpack.config.js. The loaders would check for /\.js$/ and /\.jsx$/ and assign them to babel-loader (with an exclusion of node_modules).

React

After configuring the basic presets and loaders, I added React to dependencies of the project –

$ yarn add react react-dom

 

The React related files needed to be in ./js/ directory so that the webpack can bundle it. I used the file to create a simple React app –

import React from 'react';
import ReactDOM from 'react-dom';

ReactDOM.render(
    <div>World Mood Tracker</div>,
    document.getElementById('app')
);

 

After this, I was in a stage where it was possible to use this app as a part of apps.loklak.org app. But to do this, I first needed to compile these files and bundle them so that the external app can use it.

Configuring the build target for webpack

In apps.loklak.org, we need to have a file by the name of index.html in the app’s root directory. Here, we also needed to place the bundled js properly so it could be included in index.html at app’s root.

HTML Webpack Plugin

Using html-webpack-plugin, I enabled auto building of project in the app’s root directory by using the following configuration in webpack.config.js

...
const HtmlWebpackPlugin = require('html-webpack-plugin');
const HtmlWebpackPluginConfig = new HtmlWebpackPlugin({
    template: './js/index.html',
    filename: 'index.html',
    inject: 'body'
});
module.exports = {
    ...
    plugins: [HtmlWebpackPluginConfig]
};

 

This would build index.html at app’s root that would be discoverable externally.

To enable bundling of the project using simple yarn build command, the following lines were added to package.json

{
  ..
  "scripts": {
    ..
    "build": "webpack -p"
  }
}

After a simple yarn build command, we can see the bundled js and html being created at the app root.

Using datamaps for visualization

Datamaps is a JS library which allows plotting of data on map using D3 as backend. It provides a simple interface for creating visualizations and comes with a handy npm installation –

$ yarn add datamaps

Map declaration and usage as state

A map from datamaps was used a state for React component which allowed fast rendering of changes in the map as the state of React component changes –

export default class WorldMap extends React.Component {
    constructor() {
        super();
        this.state = {
            map: null
        };
    render() {
        return (<div className={styles.container}>
                <div id="map-container"></div></div>)
    }
    componentDidMount() {
        this.setState({map: new Datamap({...})});
    }
    ...
}

 

The declaration of map goes in componentDidMount method because it would not be possible to start the map until we have the div with id=”map-container” in the DOM. It was necessary to draw the map only after the component has mounted otherwise it would fail due to no id=”map-container” in the DOM.

Defining data for countries

Data for every country had two components –

data = {
    positiveScore: someValue,
    negativeScore: someValue
}

 

This data is used to generate popup for the counties –

this.setState({
    map: new Datamap({
        ...
        geographyConfig: {
            ...
            popupTemplate: function (geo, data) {
                // Configure variables pScore so that it gives “No Data” when data.positiveScore is not set (similar for negative)
                return [
                    // Use pScore and nScore to generate results here
                    // geo.properties.name would give current country name
                ].join('');
            }
        }
    })
});

The result for countries with unknown data values look something like this –

Conclusion

In this blog post, I explained about introducing a React based app in app.loklak.org’s angular based environment. I discussed the setup and bundling process of the project so it becomes available from the project’s external HTTP server.

I also discussed using datamaps as a visualisation tool for data about Tweets. The app was first introduced in pull request fossasia/apps.loklak.org#189 and was improved step by step in subsequent patches.

Resources

Published by

Pratyush

GSoC 2017 @fossasia | B.Tech. CSE @iiitv | OSS lover