docs(operators): add documentation for distinctUntilChanged

Author: btroncone

src/operator-docs/filtering/distinctUntilChanged.ts

@@ -1,6 +1,95 @@
 import { OperatorDoc } from '../operator.model';
 
+// ported from:
+// http://reactivex.io/rxjs/class/es6/Observable.js~Observable.html#instance-method-distinctUntilChanged
+
 export const distinctUntilChanged: OperatorDoc = {
-  'name': 'distinctUntilChanged',
-  'operatorType': 'filtering'
+  name: 'distinctUntilChanged',
+  operatorType: 'filtering',
+  signature: 'public distinctUntilChanged(compare: function): Observable',
+  useInteractiveMarbles: true,
+  parameters: [
+    {
+      name: 'compare',
+      type: 'function',
+      attribute: 'optional',
+      description:
+        'Optional comparison function called to test if an item is distinct from the previous item in the source.'
+    }
+  ],
+  marbleUrl: 'http://reactivex.io/rxjs/img/distinctUntilChanged.png',
+  shortDescription: {
+    description: `
+    Returns an Observable that emits all items emitted by the source Observable that are distinct by comparison from the previous item.
+    `,
+    extras: [
+      {
+        type: 'Tip',
+        text: `
+        <span class="markdown-code">distinctUntilChanged</span> uses
+        <a
+          href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Equality_comparisons_and_sameness"
+          target="_blank"
+          class="markdown-code">
+          ===
+        </a> comparison by default.
+       `
+      }
+    ]
+  },
+  walkthrough: {
+    description: `
+      <p>
+        This operator will compare each emitted item from the source to the previously emitted item,
+        emitting only distinct values by comparison such that:
+      </p>
+      <ul>
+        <li>
+         If a comparator function is provided, then it will be called for each item to test for whether or not that value should be emitted.
+        </li>
+        <li>
+          If a comparator function is not provided, an equality check is used by default.
+        </li>
+      </ul>
+    `
+  },
+  examples: [
+    {
+      name: 'A simple example with numbers',
+      code: `
+      Rx.Observable.of(1, 1, 2, 2, 2, 1, 1, 2, 3, 3, 4)
+       .distinctUntilChanged()
+       // displays
+       // 1, 2, 1, 2, 3, 4
+       .subscribe(x => console.log(x));
+      `,
+      externalLink: {
+        platform: 'JSBin',
+        url: 'http://jsbin.com/begerivegu/1/embed?js,console'
+      }
+    },
+    {
+      name: 'An example using a compare function',
+      code: `
+      Rx.Observable.of(
+         { age: 4, name: 'Foo'},
+         { age: 7, name: 'Bar'},
+         { age: 5, name: 'Foo'},
+         { age: 6, name: 'Foo'}
+        )
+        .distinctUntilChanged((p, q) => p.name === q.name)
+         // displays:
+         // { age: 4, name: 'Foo' }
+         // { age: 7, name: 'Bar' }
+         // { age: 5, name: 'Foo' }
+        .subscribe(x => console.log(x));
+      `,
+      externalLink: {
+        platform: 'JSBin',
+        url: 'http://jsbin.com/fibaxeriku/1/embed?js,console'
+      }
+    }
+  ],
+  relatedOperators: [],
+  additionalResources: []
 };