Learn Lodash, React-native and Xstream

How to create buttons in React Native depending on the level of desired customisability: the quick and simple Button, a more customisable Touchable, and the most customisable Pressable.

Button component is useful for quick prototyping.

TouchableOpacity is the most common way of creating buttons and other touchable areas, and is suitable for most use cases.

Pressable gives you the most control over the look and feel of your button, including customising the pressed state and text, as well as handling long presses separately from regular presses.

React Native lets you build mobile apps using only JavaScript. It uses the same design as React, letting you compose a rich mobile UI from declarative components.

react-native

Creating Buttons in React Native with Three Levels of Customization

If you already know React, then React Native is a great way to build mobile apps for iOS and Android. Of course, web and mobile apps are very different to build — but this course serves as your guide.

In this course, we’ll build a mobile app from start to release with React Native for both iOS and Android. Prior React experience is required, but you don’t have to know anything about mobile development to participate.

Throughout the course, we’ll be building a “Restaurant Review” app. We’ll use all the standard mobile UI elements like text, images, form inputs, buttons, scroll views, and icons, and we’ll show several navigation techniques like push, modal, and tabs. The app will make HTTP API calls to a server and will store data on the device with AsyncStorage. Finally, we’ll specify a custom app icon and splash screen, deploy the app to a physical device, and prepare the app for release to the App Store and Play Store or for ad-hoc release.

Build a React Native Application for iOS and Android from Start to Finish

React makes it intuitive to build real-world web application. But in reality, you need to use a host of other services to get the app in front of real users. 

This course walks you through setup and implementation to get your cloud-based application up and running. 

You’ll learn to set up:
* a new project in AWS Amplify configured to your React app
* user authentication with Amazon Cognito 
* managed GraphQL with AWS AppSync
* image storage and retrieval with Amazon S3
* text translation via Lambda functions
* and finally, deployment of your application on AWS using Amazon S3

You’ll finish the course ready to quickly and easily deploy your serverless React application, so users can start using and enjoying it right away.

Building Serverless Web Applications with React & AWS Amplify

React Navigation makes the easy things easy and the hard things possible. This course will help you understand how to customize and use React Navigation for more complex navigation patterns.

You'll learn different ways to display content within the navigators, which demonstrates the built-in customizations within React Navigation. As well as learn how to interact with different UI components within React navigation, which will help you structure your application. 

Building off this, you'll learn how you can customize the default navigator behavior to provide a custom look and feel to your React Navigation application

To succeed in this course, you’ll want a basic understanding of the React Navigation API and how to use the default navigators.

Note: React Navigation has been updated to v2. This course was recorded on v1.x and the lesson code has been updated to reflect v2. The principles and patterns taught in the videos remain valid.

React Navigation for Native Mobile Applications

React Native Video is a community supported video element for React Native. It allows for remote loading of videos and also works with the React Native asset management system to load videos. Having a flexible video component is essential to developing and enhancing your application.
Like many React Native elements, the video element is very basic and doesn't ship with anything besides a flexible API. This allows you to develop the exact layout, controls, and custom overlays to match your application.

In this course we'll take a look at a basic setup. Then explore the different ways we can load and show videos. We'll show how to use a few of the custom callbacks to overlay errors and buffering elements. Because there are no controls shipped with `react-native-video` we'll show how to write custom video controls and animate them when the video has not been interacted with.

Finally we'll cover a few common paradigms found in the wild. Including repeating background cover videos, auto-playing videos when they scroll onto the screen and auto-stopping them when they are scrolled away from.

Fundamentals of React Native Video

In this course we'll explore how to create many popular animated concepts in applications across web and mobile applications. We'll look at both simple, complex, and subtle interactions that you can use to enhance your React Native application.


This course should empower you to look at an animation in an application, break down the effect, and rebuild it in your own application.


The ultimate goal is to show how using the basic Animated calls we can build out effective and complex animations that take your application to the next level.

Real World React Native Animations

In this course we will learn and demonstrate the basic concepts of the React Native Animated API. We'll use Animated calls like `timing` and `spring` to animate style properties, and learn how to combine animations to create more complex effects. We'll learn about more advanced interactions like animations with touch events, interpolation, and flip animations. The ultimate goal is to gain an understanding of how to animate React Native Views, how you can apply them to many different types of styles, and how to enhance the experience in your application.

React is one of the web’s most popular frameworks for building JavaScript applications. 

If you know what you’re doing, React can drastically simplify how you build, use, and maintain code.

Whether you’re a React newbie or you’re ready for advanced techniques, you can level-up with egghead. Explore our in-depth courses, lessons, and community resources to build more powerful applications and crack open your career.

react

Animate React Native UI Elements

In this course we’ll explore getting started with a basic React Native application on both iOS and Android. We’ll learn about using React Native components, how to build custom components, how to layout an application using Flexbox, and how to style components.


We’ll also focus on how to use state to control components, how to persist information across application reloads with AsyncStorage, and how to inline edit in a ListView.

The ultimate goal is to gain an understanding of how to get started building simple React Native applications.

Build a React Native Todo Application

[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

If you're a web developer who has been itching to get into native development, now is your chance. In this series we'll be talking all about React Native. React Native allows you to build native iOS and Android applications in JavaScript and React.js. 

Regardless of your experience with React, or even with iOS development, my hope is that this series will be beneficial to everyone who is starting out with React Native. We'll jump straight into developing with React Native by looking first at the ecosystem of building React Native apps - including  Xcode, the iPhone simulator, live reload, debugging, and more. 

Once we get our ecosystem set up and our hello world example running using ES5, we'll jump straight into building a fully functioning iPhone app which utilizes many of the best parts of developing with React Native all while covering React.js and refactor to ES6 along the way.

React Native Fundamentals

In this lesson we'll dive into using some clever offset techniques to make a button that appears to be 3D. We'll add in some animations to control those offsets so that when our button is pressed/released the button animates in and out while playing an airhorn sound.

Create an Animated 3D Button Effect in React Native

In this video, we'll learn how to deploy an existing React Native application with user authentication powered by AWS Amplify and a navigation flow built around the authentication state using React Navigation.

Deploying Existing AWS Amplify Projects using the Amplify CLI

In this video we learn how to get started in a new React Native project using TypeScript, create types, run, & refresh the application.

Up & Running with React Native & TypeScript

In this lesson I'll show you how to override the default tab bar functionality in React Navigation v5 to open a screen as a modal rather than switch tabs.

Open a Modal from the Tab Bar in React Navigation v5

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)



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