By making use of closures and lexical scope, we can achieve "private" properties by returning objects with methods from a factory function. By defining our desired "private" variables within our factory function and accessing these variables from within our returned object's methods we create a closure and maintain unique, separate references to our "private" variables.

Let's take a closer look at using Javascript's built in Array reduce function. Reduce is deceptively simple and when harnessed correctly can achieve very powerful results. By leveraging reduce, we can answer a variety of questions on a single, simple data set. In this lesson, we'll look at how you might use Array.prototype.reduce to:

• Sum an array of numbers
• Reduce an array of objects to a sum of a given property
• Group an array of objects by key or a set of given criteria
• Count the number of objects in an array by key or a given set of criteria

In this lesson, we'll walk through installing a custom color scheme into our WebStorm IDE. Dayle Rees's daylerees/colour-schemes has a great collection of themes ready to install in different formats for various editors.

For this example, we will install the Peacocks In Space theme into an OS X WebStorm 11 EAP installation. Note: This process will be very similar (or identical) for previous versions of WebStorm and other editors in the JetBrain's family of editors.

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 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 in order to address a mutation-related "bug" caused by multiple objects "sharing" a mutable structure (array) by reference.

ES6 (ES2015) introduces a standardized module format to Javascript. We'll take a look at the various forms of defining and importing modules. Using Webpack to bundle up our modules and Babel to transpile our ES6 into ES5, we'll put this new module syntax to work within our project. Then we'll examine how to import 3rd party packages from npm, importing lodash with the _ underscore alias using the ES6 module syntax.

Refactoring is a great opportunity to learn and we have an existing Javascript function that is lengthy, hard to understand, and overcomplicated. We'll take a look at putting some of Javascript's built in Array.prototype methods to use to help us clean this up and learn by example through refactoring.

By taking a few minutes to refactor this existing code, we can get a glimpse at how we can harness the power of the Array and lean on some built in Array functions available to us in Javascript's core without any added utility libraries.

In this lesson we touch on just a few of the Array methods:

• Array.prototype.forEach
• Array.prototype.filter
• Array.prototype.some.