Update README.md

README.md

@@ -1,2 +1,67 @@
-# ipapi-nodejs
-Node.js bindings for ipapi (IP address geolocation API) - https://ipapi.co/
+
+# Node.js + ipapi (IP address location API)
+
+## Usage
+
+### From Node.js REPL
+
+```
+var ipapi = require('./ipapi.js');
+
+var callback = function(res){
+    console.log(res);
+};
+
+ipapi.location(callback)       // Complete location for your IP address
+> { 
+    ip: '50.1.2.3',
+    city: 'Wilton',
+    region: 'California',
+    country: 'US',
+    postal: 95693,
+    latitude: 38.3926,
+    longitude: -121.2429,
+    timezone: 'America/Los_Angeles' 
+  }
+
+
+ipapi.location(callback, '', '', 'ip')         // Your external IP address
+50.1.2.3
+
+ipapi.location(callback, '', '', 'city')       // Your city
+Wilton
+
+ipapi.location(callback, '', '', 'country')    // Your country
+US
+
+ipapi.location(callback, '8.8.8.8')            // Complete location for IP address 8.8.8.8
+> { 
+    ip: '8.8.8.8',
+    city: 'Mountain View',
+    region: 'California',
+    country: 'US',
+    postal: '94035',
+    latitude: 37.386,
+    longitude: -122.0838,
+    timezone: 'America/Los_Angeles' 
+}
+
+ipapi.location(callback, '8.8.8.8', '', 'city')       // City for IP address 8.8.8.8
+Mountain View
+
+ipapi.location(callback, '8.8.8.8', '', 'country')       // Country for IP address 8.8.8.8
+US
+```
+
+
+
+### With API Key
+
+API key can be specified in the following ways : 
+
+1. Inside `ipapi.js` by setting `API_KEY` variable
+2. As a function argument e.g. `ipapi.location(callback, '8.8.8.8', 'secret-key')`
+
+
+### Function arguments
+- Optional arguments (e.g. IP address, key, field) can be an empty string `''` or `undefined`