[refactor] Remove any reference to the global variable (#103)

Related #99

Author: darrachequesne

lib/browser.js

@@ -9,7 +9,7 @@ var after = require('after');
 var utf8 = require('./utf8');
 
 var base64encoder;
-if (global && global.ArrayBuffer) {
+if (typeof ArrayBuffer !== 'undefined') {
   base64encoder = require('base64-arraybuffer');
 }
 
@@ -101,9 +101,9 @@ exports.encodePacket = function (packet, supportsBinary, utf8encode, callback) {
     ? undefined
     : packet.data.buffer || packet.data;
 
-  if (global.ArrayBuffer && data instanceof ArrayBuffer) {
+  if (typeof ArrayBuffer !== 'undefined' && data instanceof ArrayBuffer) {
     return encodeArrayBuffer(packet, supportsBinary, callback);
-  } else if (Blob && data instanceof global.Blob) {
+  } else if (typeof Blob !== 'undefined' && data instanceof Blob) {
     return encodeBlob(packet, supportsBinary, callback);
   }
 
@@ -189,7 +189,7 @@ function encodeBlob(packet, supportsBinary, callback) {
 
 exports.encodeBase64Packet = function(packet, callback) {
   var message = 'b' + exports.packets[packet.type];
-  if (Blob && packet.data instanceof global.Blob) {
+  if (typeof Blob !== 'undefined' && packet.data instanceof Blob) {
     var fr = new FileReader();
     fr.onload = function() {
       var b64 = fr.result.split(',')[1];
@@ -210,7 +210,7 @@ exports.encodeBase64Packet = function(packet, callback) {
     }
     b64data = String.fromCharCode.apply(null, basic);
   }
-  message += global.btoa(b64data);
+  message += btoa(b64data);
   return callback(message);
 };