Stepping Up Your JS Skills

Written by Mimi Flynn

27 February 2014

Lets say you’re a front-end developer that has historically worked on marketing sites. You can make dropdown menus, modal pop-ups, animate hover states, create slideshows, etc. jQuery, with its large base of plugins, is your best friend. You’ve never written a jQuery plugin and do not fully understand what they are and how they work within the terms of Javascript.

The most complicated ‘app’ aspect of the marketing sites you’ve created are the search and contact forms and those were mostly managed by a CMS. You want a new job but all the new jobs are looking for front-end developers that build applications with complex interactions and huge Javascript codebases. The couple of interviews you’ve recently had were bad and a little embarrassing, but you feel confident in your knowledge of Javascript and your ability to learn more.

What do you need to do to step up your JS skills?


It’s hard to know where to start because you don’t know what you don’t know. Simply reading about Javascript is a great way to fill in the gaps. There are plently of free references online:

Javascript Allonge

Mozilla Developer Network JS Guide

Reading can be taken to a whole other level, though. Don’t just read books about Javascript, but, as you get to understand JS more and more through technical book, start to look at the code of the tools you currently use and look up what you don’t understand in the Mozilla Developer JS reference site.

Use the console

The Chrome console is an excellent space to test out your new JS skills.

For example, lets say you see this code:

function findWhere(objArray, find, where, is) {

    console.log('find ' + find + ' where ' + where + ' is ' + is);

    var asw = '';

    objArray.forEach(function (element, index, array) {

        if (element[where] === is) {
            asw = element[find];


    return asw;

var groupMembers= [{
        name: 'Jane Preston',
        location: 'Boise, Idaho'
    }, {
        name: 'Jonathan Maxwell',
        location: 'Manhattan, Kansas'
        name: 'Harper Ferry',
        location: 'Atlanta, Georgia'

// outputs name of person that is located in Atlanta, Georgia
findWhere(groupMembers, 'name', 'location', 'Atlanta, Georgia');

Lets say .foreach is something you’ve not seen before, go ahead and look it up.

Then, lets say you want to play with .forEach a little bit to get a better understanding of it. Open up the console in your browser, copy and paste the above function, and dream up interesting ways in which you would need to use it.

Codewars and other JS code fun

A great way to review and learn more about Javascript fundamentals is through Codewars. Sign up and do all the ‘kata’ that you can. If you Google something and use it to get through a ‘kata’ be sure you understand why it works. Don’t be lazy about this understanding. It’s really going to help once you get to writing code for real projects with real teams.

If you are a complete beginner, check out Code Combat. It makes a game of learning to code.

Don’t be afraid of the command line

A lot of the javascript frameworks that are being distributed and developed these days require that you not be afraid of the command line–or at the least can deal with your fear enough to use it.

NodeJS is javascript that runs in the command line and can even be used as a server backend. Install it and write command line scripts that do simple every day things like searching and replacing words in a text file, so that you can better understand how it works.

‘I keep getting this question about closures’

Scope is a big deal. If you don’t understand the scope of a variable in Javascript, you will run into all kinds of bugs that feel like phantoms.

Learn how to use .call and .apply and .bind and why they are necessary.

function log(){
    var args =;
    console.log.apply(console, args);
var stuff = {
    line : 'say these things',
    say :  function(name) {
        console.log(name + ' ' + this.line);

var things = {
    line: 'other things'
}, 'mimi');

var other = stuff.say.bind(stuff);

other('someone needs to');
  • Learn about prototypical inheritance

  • Learn about variable scope (hoisting, this, .call and .apply and .bind)

  • Understand why the JS tools and frameworks you use work, what problem they were created to fix, and what alternatives are available.

Modular Javascript

Modern Javascript requires a lot of code. In order to organize and maintain that code, functionality can be organized into modules that can be easily reused.

Writing Modular Javascript with AMD, CommonJS and ES Harmony


Call, Apply, and Bind

Learning Advanced Javascript

Javascript Design Patterns

Currying in Javascript