Web Components

Afcee4ad6e383e26799ff05681d1a2a5?s=47 Nikolaus Graf
September 12, 2013

Web Components

Web Components are like Lego bricks. Easy to assemble and every piece simply fits together. But there is even more to it. Being able to create your own HTML-Tags with encapsulated style & logic changes the way you think about structuring your web applications. Get a sneak peek on how to develop scalable & maintainable applications in the future.


Nikolaus Graf

September 12, 2013


  1. 3.

    How to Use <html> <head> <link rel="import" href="/path/calendar.html"> </head> <body>

    <custom-calendar></custom-calendar> </body> </html> index.html Web Components
  2. 5.

    How to Use <html> <head> <link rel="import" href="/path/to/map.html"> </head> <body>

    <open-street-map location-x=”13.252601623535156” location-y=”52.45077881417044” zoom=”5”> </open-street-map> </body> </html> index.html Web Components
  3. 9.

    Easier and Faster Prototyping <bootstrap-modal> <h2>Welcome to Berlin</h2> <open-street-map location-x=”13.252601623535156”

    location-y=”52.45077881417044” zoom=”5”> </open-street-map> </bootstrap-modal> Web Components
  4. 10.

    Web Component • HTML Templates inert chunks of clonable DOM

    • Custom Elements create new HTML elements • Shadow DOM encapsulation & boundaries inside of DOM • HTML Imports import html documents Web Components
  5. 11.

    Client Side Templating <script id="clock-template" type="text/x-type-template"> <span class=”hour”></span>: <span class=”minute”></span>

    </script> HTML encourages run-time string parsing (.innerHTML) user-supplied data → Cross-site scripting Web Components
  6. 12.

    HTML Templates <template id="clock-tmpl"> <span class=”hour”></span>: <span class=”minute”></span> </template> <script>

    var template = document.querySelector("#clock-tmpl"); // comment is a DocumentFragment var comment = template.content.cloneNode(true); </script> Web Components HTML
  7. 13.

    HTML Templates Web Components Working directly with the DOM no

    runtime script parsing, smaller XSS attack vector Hidden from document cannot traverse into its DOM via JavaScript Content gets parsed, not rendered <script> tags aren’t executed, images aren't loaded, media doesn't play, etc.
  8. 14.

    “ ” Shadow DOM Web Components Shadow DOM gives us

    markup encapsulation, style boundaries, and exposes (to web developers) the same mechanics browsers vendors have been using to implement their internal UI. Eric Bidelman
  9. 17.

    Shadow DOM <div id="clock"></div> <script> var host = document.querySelector('#clock'); //

    use webkitCreateShadowRoot for now var shadowRoot = host.createShadowRoot(); shadowRoot.innerHTML = "<span>14</span>: <span>30</span>"; </script> Web Components HTML
  10. 18.

    Shadow DOM <h2>Black header</h2> <script> var host = document.createElement('div'); var

    shadowRoot = host.createShadowRoot(); var content = "<style>h2 {color: red}</style>"; content += "<h2>Red header</h2>"; shadowRoot.innerHTML = content; document.body.appendChild(host); </script> Black header Red header Web Components HTML
  11. 19.

    Shadow DOM shadowRoot.resetStyleInheritance = false; shadowRoot.applyAuthorStyles = false; @host {

    *:hover { color: red }; } <span pseudo="x-hour"></span> <my-clock id=”clock”></my-clock> <style> #clock::x-hour { color: blue; } </style> Web Components HTML Component CSS clock.html Template index.html
  12. 20.

    Custom Elements var ClockPrototype = Object.create(HTMLElement.prototype); ClockPrototype.createdCallback = function() {

    this.impl.textContent = "14:20"; }; var Clock = document.register('custom-clock', { prototype: ClockPrototype }); var clock = new Clock(); // adds <custom-clock>14:20</custom-clock> to the DOM document.body.appendChild(clock); Web Components tick_tock_clock.html
  13. 21.

    <link rel="import" href="clock.html"> <script> var link = document.querySelector('link[rel=import]'); var content

    = link.import.querySelector('#clock'); </script> HTML Imports Web Components <div id="clock"> <span class=”hour”>14</span>: <span class=”minute”>30</span> </div> clock.html index.html
  14. 22.

    Web Component Web Components <template id="clock-tmpl"> <span class=”hour”>14</span>: <span class=”minute”>30</span>

    </template> <script> var ClockProto = Object.create(HTMLElement.prototype); ClockProto.createdCallback = function() { var template = document.querySelector('#clock-tmpl'); var shadowRoot = this.createShadowRoot(); var clone = template.content.cloneNode(true); shadowRoot.appendChild(clone); }; document.register('my-clock', {prototype: ClockProto}); </script> <link rel="import" href="clock.html"> <my-clock></my-clock> clock.html index.html
  15. 24.

    Web Component (Polymer.js) Web Components <polymer-element name="my-clock"> <template> <span class=”hour”>14</span>:

    <span class=”minute”>30</span> </template> <script>Polymer('my-clock');</script> </polymer-element> <link rel="import" href="clock.html"> <my-clock></my-clock> clock.html index.html
  16. 27.

    Further Reading Web Components Web Components http://www.youtube.com/watch?v=fqULJBBEVQE https://dvcs.w3.org/hg/webcomponents/raw-file/57f8cfc4a7dc/explainer/index.html HTML Templates

    http://www.html5rocks.com/en/tutorials/webcomponents/template/ https://dvcs.w3.org/hg/webcomponents/raw-file/tip/spec/templates/index.html HTML Imports http://robdodson.me/blog/2013/08/20/exploring-html-imports/ https://dvcs.w3.org/hg/webcomponents/raw-file/tip/spec/imports/index.html
  17. 28.

    Further Reading Web Components Shadow DOM http://www.html5rocks.com/en/tutorials/webcomponents/shadowdom/ http://www.html5rocks.com/en/tutorials/webcomponents/shadowdom-201/ http://www.html5rocks.com/en/tutorials/webcomponents/shadowdom-301/ http://glazkov.com/2011/01/14/what-the-heck-is-shadow-dom/

    https://dvcs.w3.org/hg/webcomponents/raw-file/tip/spec/shadow/index.html Custom Elements http://www.html5rocks.com/en/tutorials/webcomponents/customelements/ https://dvcs.w3.org/hg/webcomponents/raw-file/tip/spec/custom/index.html Resources Web Components https://plus.google.com/103330502635338602217/posts Lego Bricks http://commons.wikimedia.org/wiki/File:2_duplo_lego_bricks.jpg Polymer Architecture http://www.polymer-project.org/ Icons http://pictos.cc/