update readme

Author: djih

README.md

@@ -58,14 +58,24 @@ amplitude.init('YOUR_API_KEY_HERE', 'USER_ID_HERE');
 
 # Setting Event Properties #
 
-You can attach additional data to any event by passing a Javascript object as the second argument to `logEvent`:
+You can attach additional data to any event by passing a Javascript object as the second argument to `logEvent`. The Javascript object should be in the form of key + value pairs that can be JSON serialized (we recommend using String values):
 
 ```javascript
 var eventProperties = {};
 eventProperties.key = 'value';
 amplitude.logEvent('EVENT_IDENTIFIER_HERE', eventProperties);
 ```
 
+Alternatively, you can set multiple event properties like this:
+```javascript
+var eventProperties = {
+    'color': 'blue',
+    'age': 20,
+    'key': 'value'
+};
+amplitude.logEvent('EVENT_IDENTIFIER_HERE', eventProperties);
+```
+
 # User Properties and User Property Operations #
 
 The SDK supports the operations `set`, `setOnce`, `unset`, and `add` on individual user properties. The operations are declared via a provided `Identify` interface. Multiple operations can be chained together in a single `Identify` object. The `Identify` object is then passed to the Amplitude client to send to the server. The results of the operations will be visible immediately in the dashboard, and take effect for events logged after.