Learn Electron, Flow and Mocha

Electron is a framework that makes it easy to create cross-platform desktop apps with JavaScript, HTML, and CSS. Electron and open-source tools give you everything you need to create a compelling desktop app--native user interface elements like menus and dialogs, installers, auto-updates, and more. 

This course will teach you the core concepts of Electron so that you can leverage it to create your own desktop application for macOS and Windows. 

We'll go over:
- Creating user interfaces in Electron (both HTML based and native)
- Understanding Electron's multi-process architecture 
- Shipping your app to users

Electron is a framework for creating native applications with web technologies like JavaScript, HTML, and CSS.

electron

Build a desktop application with Electron

In this lesson we’ll load javascript into the BrowserWindow and display the Electron version on the page. Loading javascript into Electron is almost exactly the same as loading it into the browser, however it is a best practice to use the `require` syntax.

Load JavaScript in an Electron BrowserWindow

A main menu is a hallmark of native desktop applications. Electron makes it easy to create native menus and menu items in JavaScript.

We’ll go over creating a menu template using `Menu.buildFromTemplate` and then setting it as the main application menu via `Menu.setApplicationMenu`. 

Create a native desktop system menu with the Electron Menu module

In this lesson we'll learn about `dialog.showMessageBox` . This is the most basic Electron dialog but it offers lots of customization options, such as `type`, `icon`, `title`, and `buttons`. Some of these options vary by platform, so we'll also look at how things differ between Windows and Mac. 

Display native desktop dialog windows with Electron

In this video, we'll learn how to save and open a file using native dialogs in Electron. First, we'll use `dialog.showSaveDialog` to display a native save dialog and use `dialog.showErrorBox` to display an error message if the save failed. Then, we'll open the file we saved using `dialog.showOpenDialog`. Finally, we'll look at how these dialogs look on Windows vs Mac.

Save/Open a file with an Electron dialog window

Dealing with multiple processes in an application is new for many JavaScript developers. We’ll go over what exactly a process is and what the primary responsibilities of the main and renderer processes are. The main process is primarily responsible for creating native UI elements and managing the application lifecycle, while the renderer process runs the HTML based UI. Accordingly, different APIs are available in each process. 

Understand Electron’s main and renderer process architecture

In Electron, we often need to coordinate actions between multiple processes. For example, if a user clicks a button in a renderer process that makes a new `browserWindow` open, we need to be able to send a message to the main process that triggers this action. We’ll look at how to do just that using the `ipcRenderer` and `ipcMain` modules.

Communicate between Electron processes using IPC

`remote` allows you to seamlessly interact with main process modules as if they were in the renderer process. It’s a super useful abstraction over IPC. We’ll learn how to use it and how to avoid some potential gotchas it has. 

[Devtron](https://electron.atom.io/devtron/) is a devtools extension that the Electron team has made. We’ll be using it to view all of the IPC that happens in our application. In this lesson we’ll learn how to include and use it in our code. 

Communicate between Electron processes using the remote module

Every Electron application needs a custom icon. Mac needs an `icns` file and Windows needs an `ico` file. We'll learn how to use a npm module, `electron-icon-maker`, that takes a 1024x1024 PNG and then outputs all the files we need. 

Create an icon for your Electron app

We’ve been running our app in a development environment using the Electron executable. Now let’s learn how to package our app into a `.app` or `.exe` file so that we can distribute it to other users. Electron doesn't provide this functionality out of the box, so we'll use a popular and easy-to-use npm package called [electron-builder](https://github.com/electron-userland/electron-builder) to handle the details. electron-builder will automatically grab our `.ico` or `.icns` file and use that as our app's icon. 

Package your Electron application into a executable file with electron-builder

Code signing ensures that your app was created and distributed by you or your company and has not been modified since it was built. It is done via a special code signing certificate issued by a trusted authority. While you can distribute your Electron app without signing it; code signing is a security best practice and is a prerequisite to implementing auto-updates in your app. We’ll walkthrough how to integrate code signing into your electron-builder build process, what happens when you don't sign your application, and how to verify it's been signed correctly. 

This lesson assumes that you have already purchased code signing certificates from Apple and one of Microsoft's trusted vendors and have exported the certificate as a `p12` or `pfx` file. 

Code sign your Electron application with electron-builder

Once users are using your app, you need a way to ship new features and fixes to them. In this lesson, we’ll learn how to implement auto-updates in your app, which allows you to distribute updates to your application seamlessly. We'll go over how to integrate with Electron's `autoUpdater` module to check for an update and display a prompt to update once it's been downloaded. For our server side implementation we'll just use a plain file server to keep things simple. 


Ship updates to your Electron app with `autoUpdater` (Mac)

In this lesson, we'll go over a few differences in implementing auto-updates on Windows like handling `Squirrel.Windows` startup events and configuring `electron-builder` to build for a `Squirrel.Windows` target.

Ship updates to your Electron app with `autoUpdater` (Windows)

flow

We'll go over some of the built-in types in Flow and how to add them to our projects by adding type annotations to our variables in JavaScript. We'll also learn about type mismatch errors when we give a variable a value that doesn't match its type annotation and how to fix it.

Primitive Types in Flow

Take the first step in learning how to create native desktop applications with Electron. We'll set up a package.json, create an npm start script to launch our app in development, and create a browser window and load a local HTML file into it.

An important concept to understand about Electron is it's multi-process architecture. The main process creates web pages by creating `BrowserWindow` instances, manages application lifecycle events, and more. Each `BrowserWindow` instance runs the web page in its own renderer process. 

Create a "Hello World" app using Electron

Mocha is a feature-rich JavaScript test framework running on Node.js and in the browser, making asynchronous testing simple and fun. Mocha tests run serially, allowing for flexible and accurate reporting, while mapping uncaught exceptions to the correct test cases.

mocha

Every dependable library needs to have tests to ensure that you don't push accidental bugs. In this lesson, see how you can set up mocha and chai to start testing your library.

Setting up Unit Testing with Mocha and Chai

Now that you've got everything set up with mocha and chai, it's time to actually write tests. In this lesson you'll learn how to use `describe` and `it` to outline your tests and make sure you don't break your library in the future.

Unit Testing with Mocha and Chai

In this lesson we'll learn how to load CSS in an Electron BrowserWindow, which is just like loading CSS into the browser. We’ll also use the `ready-to-show` event to only display our BrowserWindow when its rendering is complete.

Load CSS in a Electron BrowserWindow

Let's learn how to set up Facebook's Flow inside of a project and write a simple typecheck task that will let us run Flow against any files in our codebase.

Up and Running with Facebook Flow for Typed JavaScript

Mocha is a testing framework that provides structure for unit tests. In this lesson, we will be setting up Mocha with npm and npm scripts, writing a "Hello World" unit test, then writing the code to make the test pass (as an example of Test Driven Development (TDD), with the "red-green-refactor" workflow).

JavaScript Testing Fundamentals: Hello world unit test with Mocha (in ES6)

In this lesson, we will use Chai's request method to test our Node application's API responses.
By the end of this lesson, you will know how to:
- install the prerequisites to use mocha and chai in your application
- test for HTTP status response codes
- test for a string of text on a page
- test for a json response and validate the properties of the object
- write tests that not only verify the response of your application, but the behavior as well


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