Route change updates with React-router 4

I was updating the packages in my React bootstrap/quick start project yesterday and noticed that a totally rewritten (again) version of React-router was out. Sweet! So let’s upgrade. I’d been updating packages all morning (with the help of Version Eye) so I was ready for an end-of-the-day challenge.

The new API makes much more sense to me than the old way and I really don’t need my container anymore since you can integrate the routing components directly with the app components. “More easier to reason about.” And they’ve added components to handle change animations which I’m going to get into later today.

The one part that wasn’t clear (and wasn’t available via Google or StackOverflow) was how to listen for route changes in a component. With the earlier version (1.something or other) I was using this on my navigation bar to reflect the current route:

import {browserHistory} from 'react-router';

// React stuff 

componentDidMount() {
  browserHistory.listen((event) => {

// More React stuff

I dug into the code to find a solution and discovered this neat pub/sub system they built for it called React-broadcast. You wrap the top level in a broadcaster component and then individual components nested inside are wrapped in a subscriber component to receive updates on a specific channel. Looking at StaticRouter, the parent for the browser and hash routers, the whole route shebang is wrapped in a “location” broadcaster! So you just have to wrap the necessary components in a subscriber and you’ll get updates.

I was able to modify my code above and remove the listener and integrate it directly into my render() method:

import {LocationSubscriber} from 'react-router/Broadcasts';

render() {
  return (
    <div className="navigationbar">
      <LocationSubscriber channel="location">
      {(location) =>(
, i) => {
            return <li key={i}><Link
            className={location.pathname === item.route ? 'active' : ''}

And it works perfectly! The only gotcha is the children of the LocationSubscriber are the result of function rather than nested, but that makes sense since you’re passing the location in.

Hope this helps someone else. Is there a better way to accomplish this? Leave a comment …

I’ve stopped writing my own JavaScript framework because …

This post should have been written back in February! But I’m bad at blogging …

Rolling my own solution was a great way to quickly get up to speed on modern JavaScript syntax and best practices. I think it’s really the best way – for me. But in the end I was never going to be confident in it enough to release or suggest anyone else use it.

I was building more apps and the realization that someone was going to come behind me and maintain these things started to hit home. I’ve been in this situation before, and long term product maintenance and support wasn’t something that I wanted to get into again.

And I was job hunting. “No, I’ve never used React/Angular but I wrote my own thing …” was going to go anywhere. So I quit cold turkey and started picking up React. I’d based a lot of my methodologies on it anyway.

So that’s where I’m at now. As an e-learning developer at Red Hat, I don’t bang out code all day, but React has been great for producing apps very quickly. I’m really happy with it.

I’m writing my own JavaScript framework because …

This is a question that I “know” the answer to, but putting it down has actually been a pretty difficult. However, after discovering Tero Parviainen’s talk “Build You Own AngularJS,” I think I have a pretty good supporting reason.

Going back to my first post on this from April, I did it just to learn the basics of vanilla JS. Looking around too many people are learning frameworks and push code with them while not spending time to grok the core language. I didn’t want to be one of those and this is still true.

I’ve always liked to take things apart and discover what’s under the hood, it’s the best way to see inside of the black box. So that that’s what I’ve been doing – learning JS by looking at the internals (source, tutorials, etc.) of popular frameworks and reimplementing those in my own.

I’m building to learn. I’m building to discover and know how the shit gets done.

I’ve been focusing on React and Redux for the past few months, but I’ve never actually used them, learned how to use them on a real project. I need to get that experience add it to my resume. Not sure what my next project will be but it’ll be built with those tools and when I build it, I’ll know what’s in the box.

My framework is on GitHub.

This is cool …

Haven’t updated this in a REALLY LONG TIME, but progress on my framework is going well. I’ve definitely moved towards React with it and introduced ES6 with the help of Babel / Gulp.

I’m testing out child components and just coded up this little button thing. Really simple, but it’s damned cool to see how little coding it can take on the front end when properly support on the back side with framework architecture.

let counter = 0;

export default Nori.view().createComponent({

  getDOMEvents() {
    return {
      'click button': () => this.setProps({label:'Clicked ' + (++counter) + ' times'})

  template(props, state) {
    return this.from(`



RxJS based Pub/sub Eventing

An global eventing system is a pretty key piece of a full fledged MVC app. It lets you very easily separate concerns while maintaining communication between discrete parts of the application.

I’ve been using a simple event dispatcher for a while now. At the same time, I’ve had my eye on the excellent, and still way over my head, RxJS library. I had been using it for DOM / browser events, but I couldn’t wrap my head around how to connect event strings (“magic strings”) with an Observable and use that to execute commands or callbacks. Then I discovered this bit of sample code that demonstrated exactly what I wanted to do.

I hand’t looked at the Subject object before, but it does exactly what I need. And the callback / handler / command execute function fit right into the role of the subscribed onNext function.

Adapting the emitter example fit into my framework was straight forward and I ended up with a new Emitter module that replaces both my old EventDispatcher and EventCommandMap.

I’m keeping a simple map of subjects keyed to the event string

_subjectMap[evtStr] = {
 once: once,
 handler: handler,
 subject: new Rx.Subject()

And whenever an event is published, this object is retrieved and the subject’s subscribers are notified. If the event was only supposed to occur once, it’s unmapped safely.

function publish(evtStr, data) {
  var subjObj = _subjectMap[evtStr];

  if(!subjObj) {

  if(subjObj.once) {
    subjObj = null;

Mapping to a command module was painless as well since we just need to map the execute() function to the subject.

function subscribeCommand(evtStr, cmdModule, once) {
  var cmd = require(cmdModule);
  if(cmd.hasOwnProperty('execute')) {
    return subscribe(evtStr, cmd.execute, once);
  } else {
    throw new Error('Emitter cannot map '+evtStr+' to command '+cmdModule+': must have execute()');

Adding routes

I had a new JS project come up at work, so I’m taking time to extract my framework from the Gallery project into one that’s reusable for other projects. I should come up with a hipster name for it I suppose. Anyway, I put it on Github as App-Framework.

The Gallery didn’t need to manage multiple views and the URL routes were for  bookmarking to search results. I needed to extend my simple URL router module so that I could bind a controller function to a route change. Since I’d never done this or used a framework that did, this great post gave me a nudge in the right direction.

Setting up a route with the updated router module is pretty simple.

_router.when('/',{templateID:'test', controller:function(obj) {
  console.log('Running route: '+obj.route+', with template: '+obj.templateID);

The when method will map the route (as a key/object property) to a controller function that’s run when the URL changes. Pretty handy.

My app framework utilizes commands for controller functions, so I needed create and addition utility function on my controller to map this to a command:

function mapRouteCommand(route, templateID, command) {
  _router.when(route,{templateID:templateID, controller:function executeRouteCommand(dataObj) {

Mapping is still simple:

mapRouteCommand('/', 'defaultView', _self.RouteInitialViewCommand);
mapRouteCommand('/1', 'test1', _self.RouteOneViewCommand);

From this point, it will call a method in the AppView to load/render/show the view.

Better Modules: Hacking my way towards modularity

“A beginning programmer writes her programs like an ant builds her hill, one piece at a time, without thought for the bigger structure. Her programs will be like loose sand. They may stand for a while, but growing too big they fall apart.

Realizing this problem, the programmer will start to spend a lot of time thinking about structure. Her programs will be rigidly structured, like rock sculptures. They are solid, but when they must change, violence must be done to them.

The master programmer knows when to apply structure and when to leave things in their simple form. Her programs are like clay, solid yet malleable.”

Master Yuan-Ma, The Book of Programming


After implementing the automatic namespace import thing the other day, I wasn’t happy that I needed something this like this in the first place. Locking everything behind a rigid namespace was prohibiting reusability. I trying to move forward, but my structure was getting in the way. I’m at the middle paragraph in the quote above.

I wanted to move towards something akin to AMD or CommonJS modules, but I didn’t want to add the additional complexity of a packaging system (Browserify, Webpack, etc.) to my build process (*Why? See below …). I also wanted to know more about how they worked once all of the files are packed in a big file at the end of the process.

The Modules chapter of the Eloquent JavaScript book was a perfect place to start with this. It breaks down the logic and creation of both CommonJS and AMD modules as well as providing basic require() and define() functions. provides a more insight to how CommonJS modules work in practice also.

Ben Clinkinbeard wrote a great post explaining what the other end of Browserify looks like – how it packages all of the external files together in to one big IIFE and then pulls them out again.

With that, I wrote my own little module system – trying to follow what I was learning about CommonJS. I don’t want to lazy load all of the files so I chose to use a module ID. I’m still using my namespaces for this – it helps to keep them organized in a logical way. At least in my head.

A module skeleton

  function(require, module, exports){
    exports.myMethod = function() {};

All of the code for the modules is wrapped in a function. I’m passing in the global require function and the module and exports objects. The require() function handles that (below).

The define() function was borrowed from AMD, but it’s much simpler. It stores the modules function code in an object under the ID:

function define(id, moduleCode) {
  if(id in define.cache) {
  define.cache[id] = moduleCode;
define.cache = Object.create(null);

“Loading” a module is straight forward:

var _DOMUtils = require('nudoru.utils.DOMUtils');

The require() function looks up the ID from the define.cache, creates the exports and module objects and invokes the code. It’s also cached for performance later. The returned module is a singleton, having been cached for later use after it’s first instantiated.

function require(id) {
  if (id in require.cache) {
    return require.cache[id];

  var moduleCode = define.cache[id],
      exports = {},
      module = {exports: exports};

  if(!moduleCode) {
    throw new Error('Require: module not found: "'+id+'"');
  }, require, module, exports);
  require.cache[id] = module.exports;
  return module.exports;
require.cache = Object.create(null);

I created requireCopy() function that returns an uncached instance of the module. I’m using it for my menus when I need several unique instances of a module – one for each item.

I’m spent a few hours today refactoring my utility classes all of my components with this pattern. It’s testing out well and the resulting code is a lot cleaner. At this point, I’m not quite sure if I’m going to refactor the actual application code … But maybe I’ll feel differently on Monday.

Many thanks to Dustan Kasten for guidance on all of these module systems!

Why am I avoiding packaging?

I’m trying to keep the concat’d JavaScript file as human editable as possible. I want other people to be able to edit my code without needing to install a suite of build tools – something likely to be difficult for most people where I work.

A Tangent

While trying to figure out a problem I did something interesting in the requireCopy() function. Instead of just pulling the instance from the define cache, I created a whole new copy it with some string manipulation. I was interesting in that it did work fine, but it didn’t solve my problem so I removed it.

var funcBody = srcFunc.toString().match(/function[^{]+\{([\s\S]*)\}$/)[1],
newFuncCode = new Function('require, module, exports', funcBody);

Manipulating the function body as plain text has some interesting possibilities. It might be possible to regex the var = require() statements and make a map or perform some light dependency injection.


Namespacing Javascript Code for Great Good

Edit This didn’t last long! A day after posting this, I moved to a better, clearer, more modular pattern.


I kept my code nice and tidy while developing my app by using proper namespacing to keep it all organized under sane objects. For objects that I want to be global, I’m borrowing from Objective-C and using prefixes, so NObjThingy.

As I’m going back and fixing broken windows, I’ve taken my utility classes out of the global space and put them behind a nudoru.util.* which is great and all, but now using them is ugly


Back in AS3 land, there was true importing of other classes. Once imported, you could access their methods cleanly. I wanted something like that.

I wrote a simple function that basically does that.

function NImport(context, libArry) {
  libArry.forEach(function(lib) {
    var parts = lib.split('.'),
      obj = parts[parts.length-1];
    context[obj] = eval(lib);

Usage is simple

NImport(this, ['nudoru.utils.NLorem']);

Accessing also

console.log('lorem: '+this.NLorem.getText(3,5));

This approach has speed advantages since we they’re local variables and we don’t have to look them up. The usage of eval() is dirty, but it works out really well in this case.

Any thoughts on this approach? It’s solving an immediate problem for me, but has anyone else done this differently?

Templating improvements

Most of the visual elements in my gallery app are dynamically generated: menus, tags, item detail views and the grid of items. I’m using Underscore for this and it’s working out really well. I saw that their implementation was based on John Resig’s micro templates – which is a pretty interesting bit of JavaScript.

I made a few changes to how I’m working with the templates and wanted to document that here.

Put it in the HTML

Previously, my templates were in big strings in the JavaScript and were became very inconvenient to work around and update with structural changes. Placing the templates in the HTML makes a lot more sense and it’s easy to do. There are just a few things that you need to watch out for:

1. Place it in a <script> tag with an ID and a TYPE of ‘text/template’. As John describes on this micro template post, the type needs to be something the browser doesn’t understand and will ignore. Text/template is a logical choice.

Here’s my tag template

<script id="template__tag" type="text/template">
 <div class="tag"><%= tag %></div>

All of my template are in this file. I added an import into my main Jade file to integrate them into the final output.

2. The templates/scripts need to be in the <head> of your document. You cannot get to them with document.getElementByID() if not.

3. Trim whitespace from the beginning of the template source. If you indent the HTML under the script tag, whitespace will be present. When this is converted into a DOM element (at least by my method), it’ll be a Text node, not an Element node. A simple trim() will take care of this.

Simple templating helper module

I wrote a simple module to wrap retrieving the template HTML and the creation / processing of the Underscore template. This standardizes the way I work with the modules across my app and will make it easy to switch away from this system if I want to later.

I implemented caching on the first retrieval of the template HTML and creation of the template object. These can be expensive ops (especially creating the template object), so this saves a lot of time.

Example numbers …

The NTemplate.getTemplate function 1) gets the template HTML and 2) creates the Underscore template object. Iterating 10,000 times:

  • No cache: ~2218.643ms
  • Cache: ~0.3ms


jQuery Extraction

Relying on jQuery for DOM selection and modification still doesn’t sit right with me – It makes my feel dirty and lazy. But was incredibly convenient during the initial build of the gallery app since it allowed me to quickly “sketch” out functionality.

I’m using this post to document the changes required as I refactor jQuery out of my application let some decent DOM code in. I’m adding new utility functions to my DOMUtils file.

Quick lessons learned – I didn’t prefix my jQuery variables in any special way. Looking back I need to do this next time. Something simple like “_$varName” would have been handy. However, it’s trivial to search the project for $’s to find library calls.

Element Selection

Generally, I’m selecting elements with their ID, so this is just a simple switch to document.getElementByID(). I needed to go back up and update my RxJS observers, because these were listening to jqEl[0] to get the HTML element rather than the jQuery object. All of my JavaScript animations are handled by GSAP which takes either HTML elements or jQuery objects as arguments.

More complicated sections can be handled by the element.querySelector or element.querySelectorAll methods. Note that the latter returns a node list (array) of all matched elements. If know there is only one, you just need the first element.

So this:

_mainSearchInputEl = $('.grid__header-search input');


_mainSearchInputEl = document.querySelector('.grid__header-search > input');

Be aware: there are differences in the older get* functions and the new query* functions – both in what kind of node list they return and performance.

Viewport metrics

Whenever the window is resized or scrolled, I’m firing off an event (to a command) with the new dimensions. This is used to realign the header and footer to the new size.

Currently, I’m using this:

_currentViewPortSize = {width: $(window).width(), height: $(window).height()};

But this is just as simple:

_currentViewPortSize = {width: window.innerWidth, height: window.innerHeight};

Because of the structured needed to create the drawer for the mobile view, I’m measuring scrollTop and scrollLeft on the div that contains the gallery grid, not the body element:

var left = $(_mainScrollEl).scrollLeft(),
    top =  $(_mainScrollEl).scrollTop();


var left = _mainScrollEl.scrollLeft,
    top = _mainScrollEl.scrollTop;

Element Sizes

Rather than using $el.height() you can use el.clientHeight. el.offsetHeight returns he height including padding, borders and scroll bars.

Setting HTML


$el.html('<p>some html</p>');


htmlEl.innerHTML = '<p>some html</p>';

Adding and removing classes provides functions for adding and removing classes. I added this block to my DOMUtils functions:

hasClass: function(el, className) {
  if (el.classList) {
  } else {
    new RegExp('(^| )' + className + '( |$)', 'gi').test(el.className);

addClass: function(el, className) {
  if (el.classList) {
  } else {
    el.className += ' ' + className;

removeClass: function(el, className) {
  if (el.classList) {
  } else {
    el.className = el.className.replace(new RegExp('(^|\\b)' + className.split(' ').join('|') + '(\\b|$)', 'gi'), ' ');

toggleClass: function(el, className) {
  if(this.hasClass(el, className)) {
    this.removeClass(el, className);
  } else {
    this.addClass(el, className);

 Adding and Removing DOM Nodes

All of the nodes that I’m adding to the DOM are the results of an HTML template from Underscore.

Starting with this …

var tagel = $(_tagTemplate({tag: tag}));

The first problem is that the result from the template is an HTML string, not an element. The string must be converted to an HTML element before it can be appended to the DOM.

The DOMParser method looks like a great solution, but in testing, I found that it has issues with IE9. I found a nice little technique on a StackOverFlow tread that I turned in to a function:

function HTMLStrToNode(str) {
  var temp = document.createElement('div');
  temp.innerHTML = str;
  return temp.firstChild;

And this now works:

var taghtml = _tagTemplate({tag: tag}),
    tagnode = HTMLStrToNode(taghtml);


Comparatively, node removal is straightforward


 Wrapping an element in another

Pretty easy in jQuery:

$(el).wrapInner('<div class="floatimage__wrapper" />');

To do it without jQuery, we leverage the HTMLStrToNode function above and come up with:

wrapElement: function(wrapperStr, el) {
  var wrapperEl = DOMUtils.HTMLStrToNode(wrapperStr),
      elParent = el.parentNode;
  return wrapperEl;

Usage is easy:

DOMUtils.wrapElement('<div class="floatimage__wrapper" />', el);

Finding the closest match

jquery’s closest() function comes in really handy. I found a good native solution on this StackOverFlow thread that includes vendor prefixes since the matches() function is still relatively new.