Learn Electron, Lodash and Sequelize

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

[Lodash](https://lodash.com/docs/) is a collection of utilities that have become a staple of modern web development. This collection will show you how to re-create its most common methods using simple JavaScript techniques available in any modern web browser. In addition to re-building tools like `_.merge`, `_.get` and `_.debounce` from scratch you will also learn how to replace them completely in some cases with modern syntax such as [optional chaining](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining), [nullish coalescing](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Nullish_coalescing_operator) and [Object.fromEntries](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/fromEntries).

This collection should interest the following groups:
- Those who want to better understand common JavaScript patterns
- Engineers who want to reduce their dependence on Lodash (for performance or other reasons)
- Candidates preparing for a technical job interview (where it is common to be asked how to implement some of these methods).

JavaScript® (often shortened to JS) is a lightweight, interpreted, object-oriented language with first-class functions, most known as the scripting language for Web pages, but used in many non-browser environments as well such as node.js or Apache CouchDB. It is a prototype-based, multi-paradigm scripting language that is dynamic, and supports object-oriented, imperative, and functional programming styles.

javascript

Recreating Popular JavaScript Utility Methods from Lodash

This lesson will demonstrate how to recreate a simplified version of the popular [lodash.merge](https://lodash.com/docs/4.17.15#merge) method from scratch.

First we'll create a test file with two objects that we want to merge together and demonstrate the output after running them through lodash.merge , then we'll go about creating our own version of the function.

Our initial version will support only one `source` object to merge in, and will support only the subset of JavaScript syntax supported by the JSON spec, including the following types:
- `boolean`, `number`, `string`
- object literal
- array

After getting basic types to merge we'll show off two methods for merging arrays, either using [concat](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/concat) or recursively going through the children and merging them.

Finally we'll build our own `isObject` function to check for object literals and recursively apply our `mergeJSON` function to any object literals in our `source` object.

And last we'll add support for multiple `source` objects to be merged in using a `for...of` loop.


**Note**

The `mergeJSON` method we create approximates the `lodash.merge` functionality but does not seek to replace it. It may be useful for some use cases, but primarily it's meant to be a tool for understanding how to merge objects with recursion.

Build lodash.merge from Scratch

This lesson will demonstrate how to replace common uses of [lodash.get](https://lodash.com/docs/4.17.15#get) with [optional chaining](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining) syntax.

`_.get` is by far my favorite lodash method. I've been on so many projects where the results of a network call was a large and often unreliable blob of data. After countless attempts to reign in errors caused by trying to access non-existent properties I've come to rely on _.get as a simple & safe way to retrieve data from those objects. However, as is always the case in web development, times are changing and the tools we need to safely access properties of complex objects are now being built into the platform. [Optional chaining syntax](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining) gives us the power of _.get without several of the tradeoffs. It doesn't require an extra library to use, it plays nicely with TypeScript and it can be used when calling methods as well as when accessing properties.

This lesson covers 4 common use cases of `lodash.get` and converts them to using optional chaining syntax.

1. Nested Object and Array Access
2. String and Variable Property Access
3. Calling a Method on an Object that may Not Exist
4. Providing a Default Value when a Property does Not Exist 

---

 ### Resources

- [Nullish coalescing operator](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Nullish_coalescing_operator)

Replace lodash.get with Optional Chaining Syntax

This lesson will demonstrate how to recreate a simplified version of the popular [lodash.get](https://lodash.com/docs/4.17.15#get) method from scratch.

Our function takes 3 parameters `obj`, `string` and `defaultValue`.

The primary technique we discuss is splitting the `string` on any kind of separator we might see such as `[`, `]`, or `.` and then filtering out any empty strings we get in our array. Once we have that array of path parts, we can loop through each part with a `for..of` loop then keep reaching into object until we either a) run out of parts to try 🎉 or b) hit a dead end (`null` or `undefined`). The entire function is very simple to write, but can be incredibly powerful when you're safely trying to access large and complex blobs of data that might be coming from a database or server response. 

Build lodash.get from Scratch

This lesson will demonstrate how to recreate a simplified version of the popular [lodash.debounce](https://lodash.com/docs/4.17.15#debounce) method from scratch. **I literally failed a job interview by messing up this question, so watch carefully!**

Debounce is an incredible tool most commonly used to prevent responding too quickly to user input that is in motion. For example, preventing excessive AJAX requests made while a user types into an autocomplete field or quickly responding to window resize events without bringing your browser to a halt.

Our approach is to build the simplest `debounce` method possible using a [setTimeout](https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/setTimeout) which gets cleared each time the supplied function is called thereby delaying the execution of our function until input stops for a given amount of time.

The [Lodash implementation of debounce](https://lodash.com/docs/4.17.15#debounce) includes support for a number of options including `leading`, `maxWait`, and `trailing` which we have not covered in this video, but may in future lessons.

### Variations

Modern implementations of `setTimeout` include support for additional arguments which get passed into your function so an alternative to the approach used in this lesson would be `setTimeout(fn, wait, ...args)`

### ES5 Compatbility

If you are in an es5 environment skip the rest/spread syntax and use:

```
var args = Array.prototype.slice.call(arguments)
```

And later, in your setTimeout function:

```
fn.apply(null, args)
```

----

There are some really great resources out there to learn more about debounce, here are my two favorites:

- https://css-tricks.com/debouncing-throttling-explained-examples/
- http://benalman.com/projects/jquery-throttle-debounce-plugin/


Build lodash.debounce from Scratch

This lessons builds on [Build lodash.debounce from scratch](https://egghead.io/lessons/javascript-build-lodash-debounce-from-scratch) to add support for one of its more interesting options: `maxWait`. The `maxWait` option ensures that a debounced method is deferred no longer than the time specified. This is helpful if we need to respond to a long running interaction while it's still in progress. 

In this lesson we'll demonstrate how continuously typing into a debounced input field prevents us from logging any input at all. We'll add a `maxWait` option as a third parameter to our `debounce` function and set it up using an additional `setTimeout` call.

Essentially `maxWait` works by adding a second timer which will fire in the case that the normal debounce timer does not get called. We avoid unnecessarily triggering our debounced function by calling `clearTimeout` in both of our `setTimeout` functions to clear out whichever timer didn't just fire. We also need to set the `maxTimer` variable to `null` to tell our function it's safe to start a new maxWait timer each time either timer fires.


**Notes**

- `setTimeout` returns a timer ID not the actual timer object itself, which is why we have to `null` it out *after* we already call `clearTimeout`
- If you don't `null` out `maxTimer` in your original timer, the maxWait timer will stop triggering after the debounce timer is called the first time. I learned that one the hard way when I first recorded this video.


Extending debounce with a maxWait Option

`_.pick` and its sibling `_.omit` are popular utilities which apply filter-like functionality to objects. This lesson will demonstrate two different techniques for building the functionality found in [_.pick](https://lodash.com/docs/4.17.15#pick).

1. Using `for...of` to loop through the `keys` array
2. Using `for..in` to loop through the target object

This lesson will also cover how to emulate `_.pick`'s support for either an array or multiple arguments for the picked keys using [Rest params](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/rest_parameters) and [Array.prototype.flat()](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/flat).


Build lodash.pick from Scratch

`_.omitBy` and its sibling `_.pickBy` are popular utilities which apply filter-like functionality to objects. Both of them accept a function to determine if a given entry in the object should be included in the output object. This lesson will demonstrate an approach to build both of these utilities from a single function using the combo of `Object.entries` and `Object.fromEntries`.

`Object.entries` converts an object into an array of key, value pairs. We couple that with the native Array filter method, to create a generate `filter()` method that works on objects. Once we've filtered our object we use `Object.fromEntries` to convert the array back into an object. This works great for both `omitBy` and `pickBy`.

**Note**

`Object.fromEntries` is part of the ES2019 spec and may need [a polyfill](https://github.com/ungap/from-entries) to work depending on your environment.

---

- [MDN Guide: Object.entries](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries)
- [MDN Guide: Object.fromEntries](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/fromEntries)



Build lodash.omitBy and lodash.pickBy with Object.fromEntries

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

A modern JavaScript utility library delivering modularity, performance & extras.

lodash

This lesson shows how to refactor your old loops into using a simpler and more powerful lodash-style. We will start by looking at how many people traditionally write JavaScript `for` loops and then talk about the alternate style and benefits that Lodash offers.

Lodash: Refactoring Simple For Loops

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. 


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