Simple hello world web component

demo-shell-ng2/app/web-components/helloworld/helloworld.html

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+<!-- Defines element markup -->
+<template>
+    <p>Hello <strong></strong> :)</p>
+</template>
+
+<script>
+    (function (window, document, undefined) {
+        // Refers to the "importer", which is index.html
+        var thatDoc = document;
+
+        // Refers to the "importee", which is src/hello-world.html
+        var thisDoc =  (thatDoc._currentScript || thatDoc.currentScript).ownerDocument;
+
+        // Gets content from <template>
+        var template = thisDoc.querySelector('template').content;
+
+        // Creates an object based in the HTML Element prototype
+        var MyElementProto = Object.create(HTMLElement.prototype);
+
+        // Creates the "who" attribute and sets a default value
+        MyElementProto.who = 'World';
+
+        // Fires when an instance of the element is created
+        MyElementProto.createdCallback = function() {
+            // Creates the shadow root
+            var shadowRoot = this.createShadowRoot();
+            // Adds a template clone into shadow root
+            var clone = thatDoc.importNode(template, true);
+            shadowRoot.appendChild(clone);
+            // Caches <strong> DOM query
+            this.strong = shadowRoot.querySelector('strong');
+            // Checks if the "who" attribute has been overwritten
+            if (this.hasAttribute('who')) {
+                var who = this.getAttribute('who');
+                this.setWho(who);
+            }
+            else {
+                this.setWho(this.who);
+            }
+        };
+        // Fires when an attribute was added, removed, or updated
+        MyElementProto.attributeChangedCallback = function(attr, oldVal, newVal) {
+            if (attr === 'who') {
+                this.setWho(newVal);
+            }
+
+            if (attr === 'text') {
+                this.setWho(newVal);
+            }
+        };
+        // Sets new value to "who" attribute
+        MyElementProto.setWho = function(val) {
+            this.who = val;
+            // Sets "who" value into <strong>
+            this.strong.textContent = this.who;
+        };
+        // Registers <hello-world> in the main document
+        window.MyElement = thatDoc.registerElement('hello-world', {
+            prototype: MyElementProto
+        });
+    })(window, document);
+</script>