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React PropTypes and ES6 Destructuring

Monday, April 24th, 2017

At times one may be justified in the argument that cognitive (over)load is just an expected part of the overall developer experience. Fortunately, there are numerous steps we can take to minimize the general noise which tends to distract our intended focus. One particularly simple – yet effective – example is to remove unnecessary redundancy wherever possible. In doing so, we afford both our peers and ourselves a codebase which, over time, becomes considerably easier to maintain.

For instance, when performing code reviews, more often than not I tend to see considerable redundancy when specifying React PropTypes. Typically, something along the lines of:

As can be seen, with each new prop we are redundantly referencing React PropType lookup paths. And, while the ideal components will have a limited number of props (either connected directly, or passed down), the redundancy still remains for any component which references the same prop type. Considering the number of components a given application may contain, we can rightfully assume that the above redundancy will grow proportionally.

With the above in mind, we can easily reduce the redundancy (as well as micro-optimize the lookup paths) be simply destructuring the props of interest as follows:

While I would consider the above to be simplified enough; one could also take this a step further and destructure the isRequired props, which, in some circumstances, may be useful as well:

Admittedly, this example is rather straight-forward; however, it does help to emphasize the point that only through consistent vigilance can we ensure our source will continue to evolve organically while remaining as simple as possible.

React-Bootstrap ES6 Imports

Friday, August 12th, 2016

When leveraging React Bootstrap, one important consideration missing from the documentation (or perhaps, simply not emphasized enough) relates to module access when using ES6 imports.

Specifically, in the context of React Bootstrap’s “convenience components” <Component.SubComponent> (e.g. <Modal.Body>), such imports must be made explicit as they can not be resolved against their parent components during transformations of ES6 imports to CommonJS modules.

For instance, one can not reference sub-components as follows:

During transpilation, the above reference will result in Babel (specifically, the babel-plugin-transform-es2015-modules-commonjs module) causing an upstream exception:

Property object of JSXMemberExpression expected node to be of a type [“JSXMemberExpression”,”JSXIdentifier”] but instead got “MemberExpression

Fortunately, the solution to the issue is rather straight-forward; simply import the sub-component explicitly via react-bootstrap/lib , for example:

With the above example, the previous conversion errors will be resolved, and all will be well again.

Overall, I actually prefer the explicit imports (though it would be more convenient if they were exported via ‘react-bootstrap’).

And so, for the time being, a minor nuance worth noting should you find yourself trying to diagnose this issue at some point.

Simplified Partial Application with ES6

Wednesday, June 1st, 2016

When implementing Partial Application in ES6, implementations naturally become quite easier to reason about as default parameters, rest parameters and arrow functions can be leveraged to provide a much more comprehensive implementation.

While on the surface this may appear insignificant, when compared to having relied almost exclusively on the arguments object and Array.prototype to provide the same functionality in ES5, the benefits become rather apparent.

For instance, consider a simple multiply function which, depending on the arity of the invocation, either computes basic multiplication against the provided parameters, or returns a partial application. That is to say, if invoked as a unary function (single argument), the function returns a partial application (a new function which multiplies by the given argument). If invoked as a variadic function (variable amount of arguments), the function returns the product of the arguments.

In ES5, we could implement such a function as follows:

View Pen

Given the above example, in order to inspect and iterate over the provided arguments, we need to rely on the Array.prototype, specifically, we need to invoke on Array prototype in order to apply the slice method so as to convert the arguments object to an Array. Additionally, we also have to account for a default value of arguments[0] should it be omitted or NaN.

Not only does this require a superfluous amount of code, but it also results in a more complicated implementation that becomes considerably more verbose, and as a result, more difficult to reason about; especially for developers who may not be familiar with the specific mechanisms employed within the implementation.

ES6 to the rescue …

With the introduction of default parameters, …rest parameters, and Arrow Functions (fat arrows) in ES6, the implementation of the above example can be significantly reduced, and as a result, becomes considerably easier to understand, as we can simply re-write the multiply function as:

View Pen

As can be seen, implementing the multiply function in ES6 not only reduces the SLOC by 1/2 of the previous ES5 implementation, but more importantly, by using rest parameters, it allows us to determine and work with the functions arity in a much more natural way. Moreover, both iterating over the provided arguments and returning the partial application becomes considerably more concise simply by using arrow functions, and the need to account for undefined arguments becomes moot thanks to default parameters.

In addition, variadic invocations of such functions can also be simplified considerably using the ES6 spread operator. For example, in order to pass an Array of arguments to a function in ES5, one would need to call Function.apply against the function, like so:

With ES6 spread operators, however, we can simply invoke the function directly with the given array preceded by the spread operator:


Hopefully this article has shed some light on a few of the features available in ES6 which allow for writing implementations which not only read much more naturally, but can be written with considerably less mental overhead.


Wednesday, April 6th, 2016

TL;DR: In ES6, an IIFE is implemented as follows:

Unlike ES5, which is syntactically less opinionated, in ES6, when using an IIFE, parenthetical order matters.

For instance, in ES5 an IIFE could be written either as:


As can be seen in the above examples, in ES5 one could either wrap and invoke a function expression in parentheses, or wrap the function expression in parentheses and invoke the function outside of the parentheses.

However, in ES6, the former throws an exception, thus, one can not use:

But rather, the invocation must be made outside of the parentheses as follows:

As an aside for those who are curious, the syntax requirements are specific to ES6 and not a by-product of any particular transpilers (i.e. Babel, Traceur, etc.).

Polymer Behaviors in ES6

Friday, March 25th, 2016

Being a typical aspect of Object Oriented Design, inheritance, and mixins, provide the means by which modular reuse patterns can be facilitated within a given system. Similarly, Polymer facilitates code reuse patterns by employing the notion of shared behaviors modules. Let’s take a quick look at how to leverage them in Polymer when using ES6 classes.

Implementing Behaviors

Implementing a Behavior is quite simple, just define an object within a block expression or an IIFE, and expose it via a namespace, or module loader of choice:


Then, include the behavior in a corresponding .html document of the same name so as to allow the behavior to be imported by subsequent elements:


Extending Behaviors

After having defined and exposed a given Behavior, the Behavior can then be extended from element classes by defining a behaviors getter / setter as follows:

Once the behavior has been extended, simply import the behavior in the element’s template (or element bundle, etc.) and it is available to the template class:

Try it

Implementing Multiple Behaviors

Similar to individual behaviors, multiple behaviors can also be defined and extended:



In certain cases, I have found it helpful to group related behaviors together within a new behaviors (array) which bundles the individual behaviors together:

Note: As can be seen in the FourthBehavior, a behavior can also be implemented as an Array of previously defined behaviors.

Extending Multiple Behaviors

As with extending individual behaviors, multiple behaviors can also be extended using a behaviors getter / setter. However, when extending multiple behaviors in ES6, there are syntactic differences which one must take note of. Specifically, the behaviors getter must be implemented as follows:

Try it

And that’s basically all there is to it. Hopefully this article helped outline how Polymer Behaviors can easily be leveraged when implementing elements as ES6 classes. Enjoy.

Chuck Norris on Polymer

Wednesday, December 16th, 2015

For the past several months I have been evaluating potential frameworks which could facilitate the implementation of context aware Web Components such that each component can be assembled declaratively into recombinant features and higher-level applications. After a focused period of prototyping each candidate framework, Polymer 1.x has proven to be the most effective approach to satisfy these particular design goals, and many others as well.

While I have also been leveraging Angular 2 for implementing self-contained Web Applications which need not be composed outside the scope of the application’s root component / template, the requirement to provide elements which can be arbitrarily composed within an html document declaratively or imperatively independent of using any one particular framework is one which proves somewhat challenging; yet, can easily be satisfied by leveraging Web Components, and Polymer simplifies the process of doing so considerably.

Polymer 1.x

On a high-level, Polymer provides some much welcomed sugaring over the four Web Component specifications; HTML Templates, Shadow DOM, HTML Imports, and Custom Elements, respectively. The higher level abstraction and API offered by Polymer significantly simplifies the process of Web Component development, while reducing the time and effort required to meet both simple and complex use-cases alike.

Features provided out-of-the-box embrace that which developers have come to expect from a modern library or framework, such as one-way and two-way binding annotations, template helpers, a Local and Light DOM API, declarative and imperative event mappings, declared properties with observers and attribute reflection, and much more.

Add to this the growing Catalog of Elements provided by the Polymer Project, a complete Web Component Testing solution via WCT, optimization features such as Vulcanization with tooling support for Gulp, API Documentation components via Iron Component Page (though still pending ES6 Support) concise documentation with easy to use examples, and developers are afforded a rather elegant solution for building high quality, future facing Web Components, today.

In addition, Polymer comes in three specific layers, each of which builds upon the previous lower-level implementation. This allows for a nice level of flexibility in choosing the most appropriate implementation based on your specific needs. Depending on what is required, one can choose from the mirco-implementation for providing basic custom element sugaring, the mini-implementation for more advanced local DOM and life-cycle hooks, and the standard-implementation which provides the full suite of Polymer features.

Given the capabilities Polymer has to offer, as well as the growing number of organizations using Polymer, and some rather interesting applications being built with Polymer, if you haven’t already, I highly recommend given it a try.

Chuck Norris!

So what does any of this have to do Chuck Norris?

Well, nothing actually.

Except, like Chuck Norris, Polymer is cool – very cool, and so after accidentally coming across the ICNCB service, I thought a simple Web Component which displays some comical facts about Chuck Norris could serve as a useful Polymer example.

And so, if you like to laugh a bit while learning something new, feel free to clone the repo over on Github to get familiar with a few of Polymer’s general capabilities, or simply check out the app here and have a few laughs.

Coming up, Chuck Norris on Angular 2 …