Use shorter base64 based ids for device IDs (#251)

Author: Krishna Rajendran

src/amplitude-client.js

@@ -11,6 +11,7 @@ import type from './type';
 import UAParser from '@amplitude/ua-parser-js';
 import utils from './utils';
 import UUID from './uuid';
+import base64Id from './base64Id';
 import { version } from '../package.json';
 import DEFAULT_OPTIONS from './options';
 
@@ -141,7 +142,7 @@ AmplitudeClient.prototype.init = function init(apiKey, opt_userId, opt_config, o
       this.options.deviceId = (type(opt_config) === 'object' && type(opt_config.deviceId) === 'string' &&
           !utils.isEmptyString(opt_config.deviceId) && opt_config.deviceId) ||
           (this.options.deviceIdFromUrlParam && this._getDeviceIdFromUrlParam(this._getUrlParams())) ||
-          this.options.deviceId || deviceId || UUID() + 'R';
+          this.options.deviceId || deviceId || base64Id();
       this.options.userId =
         (type(opt_userId) === 'string' && !utils.isEmptyString(opt_userId) && opt_userId) ||
         (type(opt_userId) === 'number' && opt_userId.toString()) ||
@@ -885,7 +886,7 @@ AmplitudeClient.prototype.regenerateDeviceId = function regenerateDeviceId() {
     return this._q.push(['regenerateDeviceId'].concat(Array.prototype.slice.call(arguments, 0)));
   }
 
-  this.setDeviceId(UUID() + 'R');
+  this.setDeviceId(base64Id());
 };
 
 /**

src/base64Id.js

@@ -0,0 +1,12 @@
+// A URL safe variation on the the list of Base64 characters 
+const base64Chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_';
+
+const base64Id = () => {
+  let str = '';
+  for (let i = 0; i < 22; ++i) {
+    str += base64Chars.charAt(Math.floor(Math.random() * 64));
+  }
+  return str;
+};
+
+export default base64Id;

test/amplitude-client.js

@@ -130,7 +130,7 @@ describe('AmplitudeClient', function() {
 
       amplitude.init(apiKey);
       assert.equal(amplitude.options.apiKey, apiKey);
-      assert.lengthOf(amplitude.options.deviceId, 37);
+      assert.lengthOf(amplitude.options.deviceId, 22);
     });
 
     it('should accept userId', function() {
@@ -146,8 +146,7 @@ describe('AmplitudeClient', function() {
 
     it('should generate a random deviceId', function() {
       amplitude.init(apiKey, userId);
-      assert.lengthOf(amplitude.options.deviceId, 37); // UUID is length 36, but we append 'R' at end
-      assert.equal(amplitude.options.deviceId[36], 'R');
+      assert.lengthOf(amplitude.options.deviceId, 22)
     });
 
     it('should validate config values', function() {
@@ -193,7 +192,7 @@ describe('AmplitudeClient', function() {
       const stored = storage.load();
       assert.property(stored, 'deviceId');
       assert.propertyVal(stored, 'userId', userId);
-      assert.lengthOf(stored.deviceId, 37); // increase deviceId length by 1 for 'R' character
+      assert.lengthOf(stored.deviceId, 22);
     });
 
     it('should set language', function() {
@@ -918,8 +917,7 @@ describe('setVersionName', function() {
       amplitude.init(apiKey, null, {'deviceId': deviceId});
       amplitude.regenerateDeviceId();
       assert.notEqual(amplitude.options.deviceId, deviceId);
-      assert.lengthOf(amplitude.options.deviceId, 37);
-      assert.equal(amplitude.options.deviceId[36], 'R');
+      assert.lengthOf(amplitude.options.deviceId, 22);
     });
   });
 

test/amplitude.js

@@ -245,7 +245,7 @@ describe('Amplitude', function() {
 
       amplitude.init(apiKey);
       assert.equal(amplitude.options.apiKey, apiKey);
-      assert.lengthOf(amplitude.options.deviceId, 37);
+      assert.lengthOf(amplitude.options.deviceId, 22);
     });
 
     it('should accept userId', function() {
@@ -255,8 +255,7 @@ describe('Amplitude', function() {
 
     it('should generate a random deviceId', function() {
       amplitude.init(apiKey, userId);
-      assert.lengthOf(amplitude.options.deviceId, 37); // UUID is length 36, but we append 'R' at end
-      assert.equal(amplitude.options.deviceId[36], 'R');
+      assert.lengthOf(amplitude.options.deviceId, 22);
     });
 
     it('should validate config values', function() {
@@ -285,7 +284,7 @@ describe('Amplitude', function() {
       var stored = amplitude.getInstance()._metadataStorage.load();
       assert.property(stored, 'deviceId');
       assert.propertyVal(stored, 'userId', userId);
-      assert.lengthOf(stored.deviceId, 37); // increase deviceId length by 1 for 'R' character
+      assert.lengthOf(stored.deviceId, 22)
     });
 
     it('should set language', function() {
@@ -654,8 +653,7 @@ describe('setVersionName', function() {
       amplitude.init(apiKey, null, {'deviceId': deviceId});
       amplitude.regenerateDeviceId();
       assert.notEqual(amplitude.options.deviceId, deviceId);
-      assert.lengthOf(amplitude.options.deviceId, 37);
-      assert.equal(amplitude.options.deviceId[36], 'R');
+      assert.lengthOf(amplitude.options.deviceId, 22);
     });
   });
 

test/base64id.js

@@ -0,0 +1,13 @@
+import base64Id from '../src/base64Id';
+
+describe('base64Id', () => {
+  it('should return an id with length 22', () => {
+    assert.equal(base64Id().length, 22);
+  });
+
+  // If this test fails randomly it'll be frustrating to reproduce.  Ideally
+  // there would be some reproducible seed we would print for every test run.
+  it('should return an id of safe base64 characters', () => {
+    assert.equal(true, /^[a-zA-Z0-9\-_]*$/.test(base64Id()))
+  });
+});

test/tests.js

@@ -13,3 +13,4 @@ import './utils.js';
 import './revenue.js';
 import './base-cookie.js';
 import './top-domain.js';
+import './base64Id.js';