feat: add sendBeacon support

.gitignore

@@ -15,3 +15,6 @@ amplitude-segment-snippet.min.js
 package-lock.json
 amplitude.umd.js
 amplitude.umd.min.js
+amplitude.native.js
+amplitude.nocompat.js
+amplitude.nocompat.min.js

src/amplitude-client.js

@@ -212,6 +212,31 @@ AmplitudeClient.prototype.init = function init(apiKey, opt_userId, opt_config, o
     if (type(opt_callback) === 'function') {
       opt_callback(this);
     }
+
+    const onExitPage = this.options.onExitPage;
+    if (type(onExitPage) === 'function') {
+      if (!this.pageHandlersAdded) {
+        this.pageHandlersAdded = true;
+
+        const handleVisibilityChange = () => {
+          const prevTransport = this.options.transport;
+          this.setTransport(Constants.TRANSPORT_BEACON);
+          onExitPage();
+          this.setTransport(prevTransport);
+        };
+
+        // Monitoring just page exits because that is the most requested feature for now
+        // "If you're specifically trying to detect page unload events, the pagehide event is the best option."
+        // https://developer.mozilla.org/en-US/docs/Web/API/Window/pagehide_event
+        window.addEventListener(
+          'pagehide',
+          () => {
+            handleVisibilityChange();
+          },
+          false,
+        );
+      }
+    }
   } catch (err) {
     utils.log.error(err);
     if (type(opt_config.onError) === 'function') {
@@ -334,7 +359,9 @@ var _parseConfig = function _parseConfig(options, config) {
 
     var inputValue = config[key];
     var expectedType = type(options[key]);
-    if (!utils.validateInput(inputValue, key + ' option', expectedType)) {
+    if (key === 'transport' && !utils.validateTransport(inputValue)) {
+      return;
+    } else if (!utils.validateInput(inputValue, key + ' option', expectedType)) {
       return;
     }
     if (expectedType === 'boolean') {
@@ -511,6 +538,13 @@ AmplitudeClient.prototype._sendEventsIfReady = function _sendEventsIfReady() {
     return true;
   }
 
+  // if beacon transport is activated, send events immediately
+  // because there is no way to retry them later
+  if (this.options.transport === Constants.TRANSPORT_BEACON) {
+    this.sendEvents();
+    return true;
+  }
+
   // otherwise schedule an upload after 30s
   if (!this._updateScheduled) {
     // make sure we only schedule 1 upload
@@ -960,6 +994,25 @@ AmplitudeClient.prototype.setDeviceId = function setDeviceId(deviceId) {
   }
 };
 
+/**
+ * Sets the network transport type for events. Typically used to set to 'beacon'
+ * on an end-of-lifecycle event handler such as `onpagehide` or `onvisibilitychange`
+ * @public
+ * @param {string} transport - transport mechanism to use for events. Must be one of `http` or `beacon`.
+ * @example amplitudeClient.setDeviceId('45f0954f-eb79-4463-ac8a-233a6f45a8f0');
+ */
+AmplitudeClient.prototype.setTransport = function setTransport(transport) {
+  if (this._shouldDeferCall()) {
+    return this._q.push(['setTransport'].concat(Array.prototype.slice.call(arguments, 0)));
+  }
+
+  if (!utils.validateTransport(transport)) {
+    return;
+  }
+
+  this.options.transport = transport;
+};
+
 /**
  * Sets user properties for the current user.
  * @public
@@ -1609,11 +1662,13 @@ AmplitudeClient.prototype.sendEvents = function sendEvents() {
 
   // We only make one request at a time. sendEvents will be invoked again once
   // the last request completes.
-  if (this._sending) {
-    return;
+  // beacon data is sent synchronously, so don't pause for it
+  if (this.options.transport !== Constants.TRANSPORT_BEACON) {
+    if (this._sending) {
+      return;
+    }
+    this._sending = true;
   }
-
-  this._sending = true;
   var protocol = this.options.forceHttps ? 'https' : 'https:' === window.location.protocol ? 'https' : 'http';
   var url = protocol + '://' + this.options.apiEndpoint;
 
@@ -1633,6 +1688,19 @@ AmplitudeClient.prototype.sendEvents = function sendEvents() {
     checksum: md5(Constants.API_VERSION + this.options.apiKey + events + uploadTime),
   };
 
+  if (this.options.transport === Constants.TRANSPORT_BEACON) {
+    const success = navigator.sendBeacon(url, new URLSearchParams(data));
+
+    if (success) {
+      this.removeEvents(maxEventId, maxIdentifyId, 200, 'success');
+      if (this.options.saveEvents) {
+        this.saveEvents();
+      }
+    } else {
+      this._logErrorsOnEvents(maxEventId, maxIdentifyId, 0, '');
+    }
+    return;
+  }
   var scope = this;
   new Request(url, data, this.options.headers).send(function (status, response) {
     scope._sending = false;

src/constants.js

@@ -57,4 +57,7 @@ export default {
   UTM_CONTENT: 'utm_content',
 
   ATTRIBUTION_EVENT: '[Amplitude] Attribution Captured',
+
+  TRANSPORT_HTTP: 'http',
+  TRANSPORT_BEACON: 'beacon',
 };

src/metadata-storage.js

@@ -193,7 +193,7 @@ class MetadataStorage {
         utils.log.info(`window.sessionStorage unavailable. Reason: "${e}"`);
       }
     }
-    return !!str
+    return !!str;
   }
 }
 

src/options.js

@@ -27,6 +27,7 @@ import language from './language';
  * @property {boolean} [logAttributionCapturedEvent=`false`] - If `true`, the SDK will log an Amplitude event anytime new attribution values are captured from the user. **Note: These events count towards your event volume.** Event name being logged: [Amplitude] Attribution Captured. Event Properties that can be logged: `utm_source`, `utm_medium`, `utm_campaign`, `utm_term`, `utm_content`, `referrer`, `referring_domain`, `gclid`, `fbclid`. For UTM properties to be logged, `includeUtm` must be set to `true`. For the `referrer` and `referring_domain` properties to be logged, `includeReferrer` must be set to `true`. For the `gclid` property to be logged, `includeGclid` must be set to `true`. For the `fbclid` property to be logged, `includeFbclid` must be set to `true`.
  * @property {boolean} [optOut=`false`] -  Whether or not to disable tracking for the current user.
  * @property {function} [onError=`() => {}`] - Function to call on error.
+ * @property {function} [onExitPage=`() => {}`] - Function called when the user exits the browser. Useful logging on page exit.
  * @property {string} [platform=`Web`] -  Platform device is running on. Defaults to `Web` (browser, including mobile browsers).
  * @property {number} [savedMaxCount=`1000`] -  Maximum number of events to save in localStorage. If more events are logged while offline, then old events are removed.
  * @property {boolean} [saveEvents=`true`] -  If `true`, saves events to localStorage and removes them upon successful upload. *Note: Without saving events, events may be lost if the user navigates to another page before the events are uploaded.*
@@ -35,6 +36,7 @@ import language from './language';
  * @property {number} [sessionTimeout=`30*60*1000` (30 min)] -  The time between logged events before a new session starts in milliseconds.
  * @property {string[]} [storage=`''`] - Sets storage strategy.  Options are 'cookies', 'localStorage', 'sessionStorage', or `none`. Will override `disableCookies` option
  * @property {Object} [trackingOptions=`{ city: true, country: true, carrier: true, device_manufacturer: true, device_model: true, dma: true, ip_address: true, language: true, os_name: true, os_version: true, platform: true, region: true, version_name: true}`] - Type of data associated with a user.
+ * @property {string} [transport=`http`] - Network transport mechanism used to send events. Options are 'http' and 'beacon'.
  * @property {boolean} [unsetParamsReferrerOnNewSession=`false`] -  If `false`, the existing `referrer` and `utm_parameter` values will be carried through each new session. If set to `true`, the `referrer` and `utm_parameter` user properties, which include `referrer`, `utm_source`, `utm_medium`, `utm_campaign`, `utm_term`, and `utm_content`, will be set to `null` upon instantiating a new session. Note: This only works if `includeReferrer` or `includeUtm` is set to `true`.
  * @property {string} [unsentKey=`amplitude_unsent`] - localStorage key that stores unsent events.
  * @property {string} [unsentIdentifyKey=`amplitude_unsent_identify`] - localStorage key that stores unsent identifies.
@@ -64,6 +66,7 @@ export default {
   logAttributionCapturedEvent: false,
   optOut: false,
   onError: () => {},
+  onExitPage: () => {},
   platform: 'Web',
   savedMaxCount: 1000,
   saveEvents: true,
@@ -86,6 +89,7 @@ export default {
     region: true,
     version_name: true,
   },
+  transport: Constants.TRANSPORT_HTTP,
   unsetParamsReferrerOnNewSession: false,
   unsentKey: 'amplitude_unsent',
   unsentIdentifyKey: 'amplitude_unsent_identify',

src/utils.js

@@ -108,6 +108,23 @@ const validateDeviceId = function validateDeviceId(deviceId) {
   return true;
 };
 
+const validateTransport = function validateTransport(transport) {
+  if (!validateInput(transport, 'transport', 'string')) {
+    return false;
+  }
+
+  if (transport !== constants.TRANSPORT_HTTP && transport !== constants.TRANSPORT_BEACON) {
+    log.error(`transport value must be one of '${constants.TRANSPORT_BEACON}' or '${constants.TRANSPORT_HTTP}'`);
+    return false;
+  }
+
+  if (transport !== constants.TRANSPORT_HTTP && !navigator.sendBeacon) {
+    log.error(`browser does not support sendBeacon, so transport must be HTTP`);
+    return false;
+  }
+  return true;
+};
+
 // do some basic sanitization and type checking, also catch property dicts with more than 1000 key/value pairs
 var validateProperties = function validateProperties(properties) {
   var propsType = type(properties);
@@ -269,4 +286,5 @@ export default {
   validateInput,
   validateProperties,
   validateDeviceId,
+  validateTransport,
 };

test/amplitude-client.js

@@ -4028,4 +4028,53 @@ describe('AmplitudeClient', function () {
       assert.isNull(amplitude._metadataStorage.load());
     });
   });
+
+  describe('beacon logic', function () {
+    it('should set default transport correctly', function () {
+      amplitude.init(apiKey);
+      assert.equal(amplitude.options.transport, constants.TRANSPORT_HTTP);
+    });
+
+    it('should accept transport option correctly', function () {
+      amplitude.init(apiKey, null, { transport: constants.TRANSPORT_BEACON });
+      assert.equal(amplitude.options.transport, constants.TRANSPORT_BEACON);
+    });
+
+    it('should set transport correctly with setTransport', function () {
+      amplitude.init(apiKey);
+      amplitude.setTransport(constants.TRANSPORT_BEACON);
+      assert.equal(amplitude.options.transport, constants.TRANSPORT_BEACON);
+
+      amplitude.setTransport(constants.TRANSPORT_HTTP);
+      assert.equal(amplitude.options.transport, constants.TRANSPORT_HTTP);
+    });
+
+    it('should use sendBeacon when beacon transport is set', function () {
+      sandbox.stub(navigator, 'sendBeacon').returns(true);
+      const callback = sandbox.spy();
+      const errCallback = sandbox.spy();
+
+      amplitude.init(apiKey, null, { transport: constants.TRANSPORT_BEACON });
+      amplitude.logEvent('test event', {}, callback, errCallback);
+
+      assert.equal(navigator.sendBeacon.callCount, 1);
+      assert.equal(amplitude._unsentEvents.length, 0);
+      assert.isTrue(callback.calledOnce);
+      assert.isFalse(errCallback.calledOnce);
+    });
+
+    it('should not remove event from unsentEvents if beacon returns false', function () {
+      sandbox.stub(navigator, 'sendBeacon').returns(false);
+      const callback = sandbox.spy();
+      const errCallback = sandbox.spy();
+
+      amplitude.init(apiKey, null, { transport: constants.TRANSPORT_BEACON });
+      amplitude.logEvent('test event', {}, callback, errCallback);
+
+      assert.equal(navigator.sendBeacon.callCount, 1);
+      assert.equal(amplitude._unsentEvents.length, 1);
+      assert.isFalse(callback.calledOnce);
+      assert.isTrue(errCallback.calledOnce);
+    });
+  });
 });