Post on 11-Jul-2015
Reaching for the Future With Web Components and Polymer
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Michael Labriola - @mlabriolaSenior Consultant w/ Digital Primates
Web Components
Put simply, Web Components are an attempt to let you write custom components that can be used like this:
<body>
Sales:<br>
<my-super-cool-chart id="coolChart">
</ my-super-cool-chart >
</body>
What in the world is Polymer?
A library built on top of Web Components.
Allows us to use Web Components today in modern browsers
3 main pieces• A set of polyfills
• Web application framework
• Set of UI components
What are we going to cover?
Web Components, specifically:
What in the world are web components?What problem are they trying to solve?How do they work?Can I actually use these things?What does it mean to my app/development process?
Bleeding Edge
Web Components are beyond leading edge.
As of this moment, they do not work in their entirety in any browser
A good portion of the functionality is available in Chrome Canary if you turn on all of the experimental WebKit and JavaScript features
Why am I talking about this?
I do believe web components are a significant part of our future
I think understand their goal and vision is crucial to the next few years
I think they will change a lot before they are final
...and?
You can still play with flavors of Web Components to a large extent through polyfills today
Unless you skydive to work or love framework code more than sleep, you may want to avoid putting this all into production today
Given that... Why Components?
A few minor reasons you may like the idea, first:
Encapsulation• Manageable Reuse• Hiding complexity and implementation• Dealing with duplicated IDs• Dealing with CSS scoping / propagation
Why?
And then:
[More] even playing field• Using the same tricks the browser uses
Ease of distribution
Appropriate technology uses• Markup in markup not strings or code
How do they work?
Web Components are a draft specification, but they rely on a number of other puzzle pieces, including:
TemplatesDecoratorsShadow DOMImportsCustom Elements
Templates
The concept of templates is prolific and nearly self-explanatory. Their use takes a bit more effort:
Inactive DOM FragmentEasily Clone-ableEasily Change-able
State of the Intersection
People use templates today, they tend to take on two forms, first:
<div id="productTemplate" style="display:none">
<img src="/images/products/{{product_id}}.png">
<div class="name"></div>
<div class="description"></div>
</div>
The Reality
Which, as Eric Bidelman of Google nicely points out:
Is good, because were are creating markup in markup and working with the DOM
Is bad, because its active DOM, so the image still tries to load on startup
• 404 (Not Found) http://localhost/images/products/%7B%7Bproduct_id%7D%7D.png
Is bad, because either we deal with global styles for these things or we have to scope all of our styles manually and deal with collisions
State of the Intersection
Second form, we use strings:
<script id="productTemplate" type="text/x-template">
<img src="/images/products/{{product_id}}.png">
<div class="name"></div>
<div class="description"></div>
</script>
ORtemplate = "<div> \
<img \ src=\"/images/products/{{product_id}}.png\"> \
<div class=\"name\"></div> \
<div class=\"description\"></div> \
</div>";
The Reality
Which makes me sad…
•String parsing•No real way to do validation•Especially if stored remotely, is a great way to open yourself up to attacks
Built In Templates
You define them with the template element
<template id="productTemplate">
<div>
<img src="">
<div class="name"></div>
<div class="description"></div>
</div>
</template>
This is parsed but it’s not active. It’s not rendered.
Using It
DEMO, if you will
Decorators
Decorators are the next concept in the web component stack but…
“Decorators, unlike other parts of Web Components, do not have a specification yet.” –W3C
…so, lets go ahead and skip these for today.
Shadow DOM
Shadow DOM is at the heart of the whole component concepts
It’s encapsulation.
Its used by the browsers today to implement their own controls
Ultimately its about hiding implementation details and exposing an interface… music to my ears
Shadow DOM
The name and the technical explanation sometimes get in the way of the concept.
Put simply, the user sees this:
Photo by Photo by: Mark Kaelin/TechRepublic
Shadow DOM
The browser sees this:
Photo by Photo by: Mark Kaelin/TechRepublic
Shadow Host/Root
Rendering
The Shadow also forms a boundary. Styles don’t cross unless you let them. So you to keep control of this area
Styles
This, by default, goes both ways… meaning we aren’t worried about collisions.
Styles
Outside styles don’t affect shadow content
Styles defined in here are scoped locally
Another DEMO, please
Shadow DOM Demo
HTML Imports
HTML imports are about importing and sharing HTML content.
Why? Well, reuse, it facilitates the reuse of templates and provides us a fundamental need if we are going to share an encapsulated chunk we might call a component.
<link rel="import" href="goodies.html">
HTML Imports
Last word on this…
Imports aren’t supported pretty much anywhere yet, however, there are polyfills.
Imports are blocking. So, your page will act as though it needs this content before it can render.
Custom Elements
Elements are the key to putting this together.
Custom Elements are DOM elements that can be defined by a developer.
They are allowed to manage state and provide a scriptable interface.
In other words, they are the shell of what will become our component
Custom Elements
Defining a custom element like this:
<element extends="button" name="fancy-button">
</element>
Allows you to use that custom element in your own markup:
<div>
<fancy-button></fancy-button>
</div>
Custom Elements
You can use the concepts we previously discussed, templates, Shadow DOM, etc. from within a custom element.
Further, custom elements give you a set of Lifecycle callbacks so you can know things like when you are inserted into the DOM, removed and ready.
This means you can define the visual aspects of a custom element in mark up and the code in script.
Custom Element in Script
You can also register custom elements in script directly using:
document.register( 'option-group' );
Which turns out to be a really convenient thing because…
Reality Check
Most of this doesn’t work at all.
More specifically, the <element> approach to building your custom elements doesn’t work yet.
In fact, it seems to have left Chrome Canary for the moment.
Light, tunnel, something
This is where Polymer and other polyfills (such as x-tags) come in
They let us play today and give feedback for tomorrow
Please remember, this is pre-alpha software
In the meantime… explore
http://www.polymer-project.org/
http://www.x-tags.org/
http://www.w3.org/TR/2013/WD-components-intro-20130606/
Reaching for the Future With Web Components and Polymer
Page 0 of 59
Michael Labriola - @mlabriolaSenior Consultant w/ Digital Primates