new.target sample

new-target-es6/README.md

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+new.target Sample
+===
+See https://googlechrome.github.io/samples/new-target-es6/index.html for a live demo.
+
+Learn more at https://www.chromestatus.com/feature/5210159227863040

new-target-es6/index.html

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+---
+feature_name: new.target
+chrome_version: 46
+feature_id: 5210159227863040
+---
+
+<h3>Background</h3>
+<p>
+  The <a href="http://www.ecma-international.org/ecma-262/6.0/#sec-meta-properties-runtime-semantics-evaluation"><code>new.target</code></a>
+  value is part of the ES2015 (formerly known as ES6) specification, and can take one of two values:
+</p>
+<ul>
+  <li>
+    Inside of a constructor, <code>new.target</code> is set to a reference to the constructor that
+    was used when calling <code>new</code>.
+  </li>
+  <li>
+    Inside of a normal function, <code>new.target</code> is set to <code>undefined</code>.
+  </li>
+</ul>
+<p>
+  <code>new.target</code> is useful for distinguishing at runtime whether code is being executed as
+  a constructor or as a function. It is also handy as a way to determine to the specific subclass
+  that was used with <code>new</code> from within a superclass constructor.
+</p>
+
+{% include output_helper.html %}
+
+{% capture js %}
+class Parent {
+  constructor() {
+    // new.target is a constructor reference, and new.target.name is human-friendly name.
+    ChromeSamples.log('Hello from Parent! I was constructed via new ' + new.target.name + '()');
+  }
+}
+
+class FirstChild extends Parent {}
+
+class SecondChild extends Parent {}
+
+function notAConstructor() {
+  ChromeSamples.log('Hello from notAConstructor()! My new.target ' + new.target);
+}
+
+// Call all the constructors and the function when the page loads.
+new Parent();
+new FirstChild();
+new SecondChild();
+notAConstructor();
+{% endcapture %}
+{% include js_snippet.html js=js %}