Learn Chai, Greensock and Immutable

Animations attract the eye and add a higher level of engagement for your users. But they’re not easy to set up, and they don’t always look the way they should on every browser. 

Greensock is the best platform available for creating performant, highly-customizable animations. This course will walk you through the features of Greensock, including how to:

- animate an element
- manually control an animation
- animate between CSS classes

…and more, with cross-browser support to ensure your animations look sharp everywhere.

Ultra high-performance, professional-grade HTML5 animation for the modern web

greensock

Create Amazing Animations with GreenSock

Immutable.js provides many Persistent Immutable data structures including: List, Stack, Map, OrderedMap, Set, OrderedSet and Record.

immutable

There are lots of techniques for accessing data kept in your Lists. In this lesson, we will compare how data stored in collections can be accessed directly in both standard Arrays and ImmutableJS Lists. We will also look at how to find data inside an Immutable List using the `findEntry` and `findIndex` methods.

Get items in an ImmutableJS List

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

The reduce function in ImmutableJS allows you to transform and create new data from an existing data structure. In this example, we will do some math and calculate a sum based on data in an ImmutableJS Map.

Calculate a sum using reduce in ImmutableJS

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

The key to being productive with Immutable JS is understanding how to update values that are nested. Using `setIn` you can place a new value directly into an existing or new path. If you need access to the previous value before setting the new one, you can use `updateIn` instead. `updateIn`  accepts the same path lookups as `setIn`, but gives you a callback function instead so that you can use the previous value however you wish and return an updated version.

Updating nested values with ImmutableJS

ImmutableJS reduce functions can be nested to get data out of complex data structures. In this example, we will create an Immutable List from an Immutable Map that is nested inside of an Immutable List that is itself nested inside of an Immutable Map.

Create a list with nested reduce functions in ImmutableJS

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

By utilizing immutable data structures, we can write code that is easier to reason about, avoid mutation-related bugs, reduce complexity, and even gain some performance benefits along the way.

Before diving too far into Facebook's [Immutable.js](https://facebook.github.io/immutable-js/) library, let's take a moment to examine some of the pains and obstacles that mutable data structures present. 

We'll take a brief glimpse at putting the Immutable "List" data structure to work by example. We will convert our usage of Javascript's native `Array` to use [Immutable.List](https://facebook.github.io/immutable-js/docs/#/List) in order to address a mutation-related "bug" caused by multiple objects "sharing" a mutable structure (array) by reference.

Immutable.js: Introduction - Easing the Pains of Mutability

In this lesson, we will look at Greensock's Draggable API. We will implement a scrollable `<div>` container and explore some options available.

Create scrollable DOM elements with Greensock

In this lesson we'll look at some of the differences between standard JavaScript Arrays and Immutable Lists. We'll create Immutable.JS Lists from scratch, as well as by converting regular Arrays. We will also compare and contrast the `push` and `concat` methods between both types of collection.

Create an immutable List using Immutable.js

Modern development requires modern tooling. Rather than adding GreenSock as a script to an HTML page, we're going to install GreenSock using Yarn and set up our development environment using Parcel. This will allow us to quickly iterate and test out our animation ideas. GreenSock is abbreviated as `gsap` when importing.

Setup GreenSock as a Module with Parcel

Animating an element to a click event is as simple as passing the x and y coordinates of the click event to the properties of the `TweenMax.to` call. To be able to center the element where the mouse clicks, you also need to adjust the special xPercent and yPercent properties so the element is properly offset.

Animate and Center an Element to a Click Event with GreenSock

Rotating an element with GreenSock is as simple as changing the `rotation` property using `TweenMax`. But there's also a hugely convenient trick using the `+=` or `-+` syntax as a string that allows you to adjust based on the previous value of the rotation.

Rotate an Element Based on Previous Values with GreenSock

Animations often have multiple steps. GreenSock makes this simple with the concept of a timeline where you code each point you want your element to move to. This lesson will show you how to set up a timeline as well as pause and resume the timeline animation.

Create Animation Steps with GreenSock's Timeline

You often need to pause or resume an animation based on whether or not the current animation running. The `isActive()` getter returns a boolean that provides you with that information (the opposite information can be found with using the `paused()` getter).

Pause or Resume an Animation by Checking isActive with GreenSock

GreenSock also supports the ability to animate `from` a variable point to the current point. If you think `to` starts at a static point and moves to a variable point then `from` essentially does the opposite. `fromTo` supports the scenario where both points are variables and requires passing in a "from" set of properties and a "to" set of properties.

Animate From a Variable Point with from and fromTo in GreenSock

Each animation can be moved to a specific point in time based on the `progress` setting between 0 and 1 (0% and 100%). This lesson shows how to control the progress using the scroll wheel of the mouse which can easily fast-forward or rewind through the timeline.

Manually Control the Animation with progress in GreenSock

Any GreenSock animation can accept an array of dom elements. This lesson shows you how to easily create and tween 100 divs to the same point.

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