update whisper

docs/_whisper/Whisper-js-example.md

@@ -0,0 +1,43 @@
+---
+title: Whisper JavaScript example
+---
+
+[This link](https://github.com/gballet/whisper-chat-example) contains a full-fledged example of how to use Whisper in a small chat application.
+
+Let's now have a look at the `sendMessage` function:
+
+```javascript
+sendMessage() {
+    // Start by declaring the message, we picked a JSON format with
+    // `text` as the content and `name` as the name of the user who
+    // is sending the message.
+    let msg = {
+        text: this.text,
+        name: this.name
+    };
+
+    // (code elided for clarity)
+
+    // Create the data object that will be sent to the RPC endpoint.
+    let postData = {
+        ttl: 7,
+        topic: '0x07678231',
+        powTarget: 2.01,
+        powTime: 100,
+        payload: encodeToHex(JSON.stringify(msg)),
+    };
+
+    // Set the appropriate key id.
+    if (this.asym) {
+        postData.pubKey = this.recipientPubKey;
+        postData.sig = this.asymKeyId;
+    } else
+        postData.symKeyID = this.symKeyId;
+
+    // Perform the RPC call that will tell the node to forward
+    // that message to all its neighboring nodes.
+    this.shh.post(postData);
+
+    // (code elided for clarity)
+}
+```