Gain insights into intermediate JavaScript, mastering interview questions, common design patterns, and deep understanding of the language. Learn with expert Arnav Aggarwal's engaging teaching method.

This is for those familiar with the basics of JavaScript and looking to advance their knowledge and really understand how the language works. We'll cover topics that are essential to help you read, understand, and write better code. Before starting, you should be familiar with the basics of variables, functions, and loops in JavaScript.

This course will enable you to master JavaScript interview questions that stump most developers. You'll be able to talk intelligently about the fundamentals of the language and about common design patterns.

This course has been created by Arnav Aggarwal, a full-stack engineer. Having attended a coding boot camp and having taught at another one, Arnav has extensive experience understanding how new developers learn to code. In under a month, Arnav's published articles on JavaScript concepts have received over 50,000 views and have been featured as staff selections on Medium.com and codementor.io because of their educational value.

Yangshun Tay

In response to "The Complete Rules to 'this'": 
Clear and to the point. This is one of the best explanations on “this” available on the net. I particularly liked how you explained about global function invocation being implicit method invocation on window. Thank you.

Front-End Engineer at Facebook

Jaya Arasalike

This is an excellent javascript course. Arnav covers deep basics well by giving enough examples and explaining what exactly is happening - how/ when values are changing. His diagrams, for example local vs global scope or the table representation for values vs reference makes reader easily understand what he is talking about and how it works. The quizzes at the end of each chapter, makes one think through what he or she has learnt and apply those concepts to arrive at the answers. That helps a lot in nailing down the core concepts. 

Bootcamp Graduate & Full-Stack Developer

Irshaad Bijan Adatia

In response to the Prototypes & Inheritance articles:

Having just finished a JavaScript course in college, this was a great stepping stone to move into an intermediate level if JS. Thank you.

It was also very well laid out.

Computer Science Student

Step Up Your JS: A Comprehensive Guide to Intermediate JavaScript

# Array.filter

The idea here is similar to Array.map, except instead of transforming individual values, we want to filter existing values. Without any functions (besides [Array.push](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/push?v=example)), say we want to filter out values in an array that are less than 5:

## for-loop

Learn how `Array.filter` works by learning how to write it yourself. It's almost as powerful as `map` and used ubiquitously throughout code.

Behavior of Functions and Variables

Essential Modern JavaScript - ES2015+ In Depth

Object Oriented Programming: The Core

Object Oriented Programming: `this` and Inheritance

Introduction to Functional Programming

Functional Programming: Arrays and their Powerful Methods

Functional Programming: Objects and their Powerful Methods

A Dive into Asynchronous JavaScript

Advanced Modern JavaScript - Cutting Edge ES2015+

Conclusion

Filter

Array.filter