Add Computed Property Names In ES6 as a JavaScript til

javascript/computed-property-names-in-es6.md

@@ -0,0 +1,37 @@
+# Computed Property Names In ES6
+
+Perhaps more often than not, property names in an object are based on
+something dynamic rather than a static value. In ES5, you may end up with
+code like the following to build an object with dynamic property names:
+
+```javascript
+var dynamic1 = 'hello',
+  dynamic2 = 'world';
+var obj = {};
+var propName1 = dynamic1 + dynamic2;
+var propName2 = 5 * 11;
+obj[propName1] = true;
+obj[propName2] = false;
+
+> obj
+// { 55: false, 'helloworld': true }
+```
+
+With ES6, we get _computed property names_ which allow us to do all of these
+inline when defining the object. We just have to wrap the code that will be
+evaluated to a property name in brackets:
+
+```javascript
+const dynamic1 = 'hello',
+  dynamic2 = 'world';
+const obj = {
+  [dynamic1 + dynamic2]: true,
+  [5 * 11]: false
+};
+
+> obj
+// { 55: false, 'helloworld': true }
+```
+
+Computed properties are [already available in many modern
+browsers](https://kangax.github.io/compat-table/es6/#test-object_literal_extensions_computed_properties).