Learn Chai, Mobx and Ruby

Developing logic-rich applications is a key skill to have.

The TypeScript–React combination helps you unlock that skill, and it’s a great developer experience in terms of writing understandable and refactorable HTML. But the default state management for React has a long way to go to feel simple and maintainable — and that’s where MobX makes your life so much easier. MobX keeps things simple without using complicated setups like `provider` and `connect` that provide way too little value for all the mental overhead. 

In this course, you’ll see how to model your React application logic using simple JavaScript classes — and with the help of MobX, make those classes the beating heart of your React applications. You’ll learn:

- that you don't need advanced annotations and TypeScript features to use MobX
- how to easily refactor code through TypeScript
- how to use TypeScript to track the flow of state as properties change

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

Develop React Applications with Mobx and TypeScript

MobX State Tree (MST) is a library that helps you organize your application states in a very structured manner. It allows you to create a component model, but for your data!

Course instructor Michel Weststrate—creator of Mobx—will teach you to model application state after your problem domain with MST. You will get hands-on practice and see how MST lets you solve problems with its out-of-the-box support for asynchronous actions, patches, snapshots, and middleware.

Over the 17 lessons, you’ll build a little bookshop application using React, MST, and create-react-app, while learning how to manage the lifecycle of your data by describing data models. 

Join Michel in one of the most popular courses on egghead!

Manage Application State with Mobx-state-tree

MobX is designed to enable building web applications with a complex data model in an intuitive and very performant manner. Using React and MobX is currently the simplest way to build component based web applications.

"Half the code, twice the fun" is how people describe MobX, or "So simple, I cannot believe it just works". 



Manage Complex State in React Apps with MobX

Applications are driven by state. Many things, like the user interface, should always be consistent with that state.
[MobX](https://mobxjs.github.io/mobx) is a general purpose FRP library that provides the means to derive, for example, a React based user interface automatically from the state and keep it synchronized.

The net result of this approach is that writing applications becomes really straight-forward and boilerplate free.

Sync the UI with the app state using MobX observable and observer in React

This lesson explains how you can build larger trees of react component and how they are managed efficiently by MobX. You will learn how to pass observable data structures around in props and how the Devtools can be used to analyze the performance of your UI.

Pass observable data through props in MobX

This lesson explains how actions can be used to control and modify the state of your application. They help you to structure your code base and integrate well with the MobX React Devtools. Actions automatically create transactions, which group changes together.

Use MobX actions to change and guard state

Derivations form the backbone of MobX and come in two flavors: computed values are values that can be derived from the state automatically. And reactions can be used to manage side effects, such as drawing the user interface. In this lesson you will learn how these concepts relate to each other and how they are optimized automatically by MobX.

Derive computed values and manage side effects with MobX reactions

In this lesson we will finally do something useful with our temperatures. We extend it into a small app in which users can enter a location, which is used as input for an external API to fetch weather data. In the mean time MobX keeps our UI in sync with the current state of the request.

Handle user input and asynchronous actions with MobX

Passing down stores through each layer of components can be a tedious job. This lesson demonstrates how Provider can be used to automatically connect observer based components to stores, by leveraging React's context mechanism in the background.

Connect MobX observer components to the store with the React Provider

So far we have been talking briefly about reactions. In this lesson you will learn how reactions can be used to observe state until some condition is met. After that you will see how autorun can be used to automatically trigger side effects. This is used internally by observer as well. We will test this by replacing React with our own handcrafted rendering which is still kept in sync with the state by MobX!

Write custom MobX reactions with when and autorun

Rails is a web-application framework that includes everything needed to create database-backed web applications according to the Model-View-Controller (MVC) pattern.

rails

Expanding on [Part 1](https://egghead.io/lessons/angularjs-rails-todo-api-part-1), this lesson will look at how to bootstrap AngularJS in a rails application as part of the asset pipeline. With Angular available, you'll see how to communicate with the Rails API using $resource.

Rails Todo API Part 2

So far we have used the observable decorator extensively. Let's take a closer look on what it does and see how the extendObservable and observable functions can be used to create observable objects, arrays and maps.

Use observable objects, arrays, and maps to store state in MobX

The MobX React devtools can be used to analyze when and why React components are re-rendered. They offer three features: 1) visualize when components re-render, 2) show the dependency tree of a component, to see which data it's rendering depends upon, and 3) log in detail which data is changed by your actions, and how these changes propagate through the application.

Analyze React components with MobX-React devtools

AngularJS is an open-source JavaScript framework, maintained by Google, that assists with running single-page applications. Its goal is to augment web-based applications with model–view–controller (MVC) capability, in an effort to make both development and testing easier.

angularjs

Rails makes an excellent choice for delivering data to AngularJS via REST apis. In this first lesson of a two part series, you'll see how to create a simple API for CRUD operations on TODOs using Rails. This isn't an introduction to Rails, and assumes you know the basics. 

Rails Todo API Part 1

Chai is a BDD / TDD assertion library for node and the browser that can be delightfully paired with any javascript testing framework.

chai

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 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


Test Node RESTful API with Mocha and Chai

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

Writing great ES6 style Promises for Node.js is only half the battle. Your great modules must include tests as well to ensure future iterations don't break them. In this lesson, I show you a simple ES6 Promise in Node.js, then walk you through creating tests in Mocha using chai and chai-as-promised to test both resolve and reject methods.

Testing ES6 Promises in Node.js using Mocha and Chai

In this lesson, you will learn how to verify your API server is returning HTTP 400 responses when clients submit incorrect data. Returning HTTP 400 ensures that your clients are notified of the incorrect usage. Testing for them ensures your API returns errors instead of incorrect responses when supplied with incorrect data.

Test for HTTP 400 responses with Mocha and Chai

Create a search directive with AngularJS and Rails. You'll want to take a look at the related [Rails TODO API Part 1](https://egghead.io/lessons/angularjs-rails-todo-api-part-1) and [Rails TODO API Part 2](https://egghead.io/lessons/angularjs-rails-todo-api-part-2). This is **not** a Rails how-to, so some knowledge there is expected to get up and running.

Search Directive with Rails

In this lesson, we introduce the running example of this course, a wishlist app. We will take a look at the core of mobx-state-tree (MST), models. Models describe the shape of your state and perform type validation. 

You will learn:
* Defining models using types.Model
* Instantiating models from JSON using Model.create
* Primitive types: types.string & types.number
* Type inference for primitive types
* types.array
* types.optional
* Composing models into a model tree
* Testing models using jest

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