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Initialize JavaScript (Browser) SDK

How to initialize the Optimizely Feature Experimentation JavaScript (Browser) SDK in your application.

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Use the createInstance method to initialize the JavaScript (Browser) SDK and instantiate an instance of the Optimizely client class that exposes API methods like Decide methods. Each client corresponds to the datafile representing the state of a project for a certain environment.

Version

SDK v5.0.0-beta and higher

Description

The createInstance method accepts a configuration object to configure Optimizely Feature Experimentation.

Some parameters are optional because the SDK provides a default implementation, but you may want to override these for your production environments. For example, you may want override these to set up an error handler and logger to catch issues, an event dispatcher to manage network calls, and a User Profile Service to ensure sticky bucketing.

Parameters

The table below lists the required and optional properties of the config object:

ParameterTypeDescription
datafile
optional 		stringThe JSON string representing the project. At least one of sdkKey or datafile must be provided.
sdkKey
optional		stringThe key associated with an environment in the project. At least one of sdkKey or datafile must be provided.
eventDispatcher
optional		objectAn event dispatcher to manage network calls. An object with a dispatchEvent method.
logger
optional 		objectA logger implementation to log messages. An object with a log method.
errorHandler
optional		objectAn error handler object to handle errors. An object with a handleError method
userProfileService
optional		objectA user profile service. An object with lookup and save methods.
jsonSchemaValidator
optional		objectTo perform JSON schema validation on datafiles, import the validator from '@optimizely/optimizely-sdk/dist/optimizely.json_shema_validator.min.js', and pass it as this initialization option. Skipping JSON schema validation enhances performance during initialization.
datafileOptions
optional		objectObject with configuration for automatic datafile management. Can have autoUpdate (Boolean), urlTemplate (string), and updateInterval (number) properties.
access_token
optional		stringServer-side (only) Optimizely Feature Experimentation SDKs can use an access token (with sdk key) to fetch the datafile from an authenticated endpoint. Find your datafile access token in the Optimizely app at Settings>Environments. Select your secure environment, and copy the Datafile access token.
defaultDecideOptions
optional		ArrayArray of OptimizelyDecideOption enums. When the Optimizely client is constructed with this parameter, it sets default decide options which are applied to all the Decide calls made during the lifetime of the Optimizely client. Additionally, you can pass options to individual Decide methods (does not overrides defaults).
For example code, see OptimizelyDecideOption.
odpOptions
optional		OptimizelySdkSettingsYou must have the Optimizely Data Platform Advanced Audience Targeting integration enabled.

Returns

Instantiates an instance of the Optimizely class.

Examples

In the JavaScript SDK, you can provide either a sdkKey or datafile or both.

  • When initializing with just the SDK key, the datafile will be automatically downloaded
  • When initializing with just the datafile, the SDK will use the given datafile.
  • When initializing with both the SDK key and datafile, the SDK will use the given datafile to start, then download the latest version of the datafile in the background.

Instantiate using datafile

First, get a copy of the datafile from our server. Then, instantiate the client.

// minimal client
var optimizely = require('@optimizely/optimizely-sdk');

const rp = require("request-promise");

// Rplace <Your_SDK_Key> to get the datafile
const DATAFILE_URL =
  "https://cdn.optimizely.com/datafiles/<Your_SDK_Key.json";
const datafile = await rp({ uri: DATAFILE_URL, json: true });
console.log("Datafile:", datafile);
const optimizelyClient = optimizely.createInstance({
  datafile
});
// Use optimizelyClient to run experiments

<!--step 1: add a <script> tag in your <head> tag: 
 this adds the datafile on the window variable window.optimizelyDatafile-->

<script src="https://cdn.optimizely.com/datafiles/<Your_SDK_KEY>.json/tag.js"></script>

<!--step 2. after the <body> tag, add a new <script> tag to instantiate an Optimizely client  from the datafile:-->

<script>
    var optimizelyClient = window.optimizelySdk.createInstance({
        datafile: window.optimizelyDatafile,
    });
</script>

If you do not pass in an SDK key, the Optimizely Client will not automatically sync newer versions of the datafile. Any time you retrieve an updated datafile, just re-instantiate the same client.

For simple applications, all you need to provide to instantiate a client is a datafile specifying the project configuration for a given environment. For most advanced implementations, you'll want to customize the logger or error handler for your specific requirements.

Instantiate using SDK Key

To instantiate using SDK Key, obtain the SDK Key from your project's settings page, then pass sdkKey as a string property in the options object you pass to the createInstance method.

const optimizely = require('@optimizely/optimizely-sdk');
const optimizelyClient = optimizely.createInstance({
  sdkKey: '<Your_SDK_Key>', // Provide the sdkKey of your desired environment here
});

When you provide the sdkKey, the SDK instance asynchronously downloads the datafile associated with that sdkKey. When the download completes, the SDK instance updates itself to use the downloaded datafile. You can use the onReady promise method to wait for the datafile to be downloaded before using the instance.

const optimizely = require('@optimizely/optimizely-sdk');
const optimizelyClient = optimizely.createInstance({
  sdkKey: '<Your_SDK_Key>', // Provide the sdkKey of your desired environment here
});
optimizelyClient.onReady().then(() => {
  // optimizelyClientInstance is ready to use, with datafile downloaded from the
  // Optimizely CDN
});

For simple applications, all you need to provide to instantiate a client is a datafile specifying the project configuration for a given environment. For most advanced implementations, you'll want to customize the logger or error handler for your specific requirements.

Notes

Customize datafile management behavior

To customize datafile management behavior, provide a datafileOptions object property inside the options object passed to createInstance. The table lists the supported customizable options.

OptionTypeDescription
autoUpdatebooleanWhen true, and sdkKey was provided in createInstance options, automatic updates are enabled on this instance. The default value is false.
updateIntervalnumberWhen automatic updates are enabled, this controls the update interval. The unit is milliseconds. The minimum allowed value is 1000 (1 second). The default value is 300000 milliseconds (5 minutes).
urlTemplatestringA format string used to build the URL from which the SDK will request datafiles. Instances of %s will be replaced with the sdkKey. When not provided, the SDK will request datafiles from the Optimizely CDN.

The following example shows how to customize datafile management behavior:

const optimizely = require('@optimizely/optimizely-sdk');

const optimizelyClientInstance = optimizely.createInstance({
  sdkKey: '<Your_SDK_Key>',
  datafileOptions: {
    autoUpdate: true,
    updateInterval: 600000, // 10 minutes in milliseconds
    urlTemplate: 'http://localhost:5000/datafiles/%s.json',
  },
});

onReady details

Use the onReady method to wait until the download is complete and the SDK is ready to use.

The onReady method returns a Promise representing the initialization process.
onReady accepts an optional timeout argument (defined in milliseconds) that controls the maximum duration that the returned Promise will remain in the pending state. If timeout is not provided, it defaults to 30 seconds.

const optimizely = require('@optimizely/optimizely-sdk');
let optimizelyClient = optimizely.createInstance({
  sdkKey: '<Your_SDK_Key>',
});
optimizelyClient.onReady().then(() => {
  // optimizelyClient is ready to use, with datafile downloaded from the Optimizely CDN
});

// Provide a timeout in milliseconds - promise will resolve if the datafile still is not available after the timeout
instance.onReady({ timeout: 5000 }).then(result => {
  // Returned Promise is fulfilled with a result object
  console.log(result.success); // true if the instance fetched a datafile and is now ready to use
  console.log(result.reason); // If success is false, reason contains an error message
})

The Promise returned from the onReady method is fulfilled with a result object containing a boolean success property.

When the success property is true, the instance is ready to use with a valid datafile. When the success property is false, there is also a reason string property describing the failure. Failure can be caused by expiration of the timeout, network error, unsuccessful HTTP response, datafile validation error, or the instance's close method being called.

Set a fallback datafile

If you provide an sdkKey and a static fallback datafile for initialization, the SDK uses the fallback datafile immediately if it is valid while simultaneously downloading the datafile associated with the sdkKey. After the download completes, if the downloaded datafile is valid and has a more recent revision than the fallback datafile, the SDK updates the instance to use the downloaded datafile.

const optimizely = require('@optimizely/optimizely-sdk');
const datafile = '{"version": "4", "rollouts": [], "typedAudiences": [], "anonymizeIP": false, "projectId": "12345", "variables": [], "featureFlags": [], "experiments": [], "audiences": [], "groups": [], "attributes": [], "botFiltering": false, "accountId": "12345", "events": [], "revision": "1"}'; 
const optimizelyClient = optimizely.createInstance({
  sdkKey: '<Your_SDK_Key>',
  datafile,
});
// optimizelyClient can be used immediately with the given datafile, but
// will download the latest datafile and update itself

📘

Note

You must have the Advanced Audience Targeting integration between Optimizely Data Platform (ODP) and Optimizely Feature Experimentation enabled and set up before being able to use OdpManager.

Advanced Audience Targeting and OdpManager are currently beta. Contact your Customer Success Manager for more information or register now on Optimizely.com.

OdpManager

OdpManager contains the logic supporting Optimizely Data Platform (ODP)-related features in Optimizely Feature Experimentation, including audience segments, ODP events, and VUID management.

Initializing the JavaScript (Browser) SDK with ODP Disabled

const optimizelyInstance = optimizelySdk.createInstance({
  sdkKey: '<YOUR_SDK_KEY>',
  odpOptions: {
    disabled: true,
  },
});

Initializing the JavaScript (Browser) SDK with ODP and Custom Settings

const optimizelyInstance = optimizelySdk.createInstance({
  sdkKey: '<YOUR_SDK_KEY>',
  odpOptions: {
    // disabled: false,  // change to true to disable
    eventApiTimeout: 1000,
    eventQueueSize: 1,
    // eventRequestHandler: new BrowserRequestHandler(),
    // eventManager: new OdpEventManager(),
    segmentsApiTimeout: 1000,
    segmentsCacheSize: 10,
    segmentsCacheTimeout: 1000,
    // segmentsCache: new ICache<string, string[]>(),
    // segmentsRequestHandler: new BrowserRequestHandler(),
    // segmentManager: new OdpSegmentManager(),
    
  },
});

📘

Note

Unlike other Feature Experimentation SDKs for Advanced Audience Targeting, the JavaScript (Browser) cannot batch events. Because of that limitation, you cannot update the following:

  • eventBatchSize – will always be set to 1
  • eventFlushInterval – will always be set to 0

Calling getVuid() after the client successfully initializes

// After successfully initializing the JavaScript (Browser) SDK...
const deviceVuid = optimizelyInstance.getVuid();  
console.log('Device VUID: ${deviceVuid}');

For information see VUIDs and client-side SDKs.

Customize OdpManager

Using the parameters in odpOptions, you can customize the behavior of the ODP event and segment managers, even going as far as being able to replace them with your own implementations if desired.

Example odpOptions w/Custom Event Manager

odpOptions: {
  // …
  eventManager: new OdpEventManager({
    odpConfig, // new OdpConfig()
    apiManager, // new OdpEventApiManager()
    logger, // new LogHandler()
    clientEngine: 'javascript-sdk',
    clientVersion: '5.0.0',
    batchSize: 10, // Cannot change in JavaScript (Browser) environment.
    flushInterval: 2000, // Cannot change in JavaScript (Browser) environment.
  }),
},

Customize OdpEventApiManager

OdpEventApiManager is an interface, and its implementation requires the user to provide the functionality of the following methods:

export interface IOdpEventApiManager {
  sendEvents(apiKey: string, apiHost: string, events: OdpEvent[]): Promise<boolean>;
}

Example odpOptions w/Custom Segments Manager

odpOptions: {  
  // ...
  segmentManager: new OdpSegmentManager(  
    odpConfig, // new OdpConfig()  
    new BrowserLRUCache<string, string[]>({  
      maxSize: 2,  
      timeout: 4000,  
    }), // new ICache<string, string[]>()  
    segmentApiManager, // new IOdpSegmentApiManager()  
  ),  
},

Customize the OdpSegmentApiManager:

export interface IOdpSegmentApiManager {  
  fetchSegments(  
    apiKey: string,  
    apiHost: string,  
    userKey: string,  
    userValue: string,  
    segmentsToCheck: string[]  
  ): Promise<string[] | null>;  
}

Custom cache

You can provide a custom cache, which will be used to store the fetch_qualified_segments results. To provide a custom cache, you should implement the following interface:

Segments Cache Interface

export interface ICache<K, V> {
  lookup(key: K): V | null;
  save({ key, value }: { key: K; value: V }): void;
  reset(): void;
}

Custom Segments Cache Implementation example from LRUCache implementation

export class LRUCache<K, V> implements ICache<K, V> {
  private _map: Map<K, CacheElement<V>> = new Map();
  private _maxSize; // Defines maximum size of _map
  private _timeout; // Milliseconds each entry has before it becomes stale

  get map(): Map<K, CacheElement<V>> {
    return this._map;
  }

  get maxSize(): number {
    return this._maxSize;
  }

  get timeout(): number {
    return this._timeout;
  }

  constructor({ maxSize, timeout }: LRUCacheConfig) {
    const logger = getLogger();

    logger.debug(`Provisioning cache with maxSize of ${maxSize}`);
    logger.debug(`Provisioning cache with timeout of ${timeout}`);

    this._maxSize = maxSize;
    this._timeout = timeout;
  }

  public lookup(key: K): V | null {
    if (this._maxSize <= 0) {
      return null;
    }

    const element: CacheElement<V> | undefined = this._map.get(key);

    if (!element) return null;

    if (element.is_stale(this._timeout)) {
      this._map.delete(key);
      return null;
    }

    this._map.delete(key);
    this._map.set(key, element);

    return element.value;
  }

  public save({ key, value }: { key: K; value: V }): void {
    if (this._maxSize <= 0) return;

    const element: CacheElement<V> | undefined = this._map.get(key);
    if (element) this._map.delete(key);
    this._map.set(key, new CacheElement(value));

    if (this._map.size > this._maxSize) {
      const firstMapEntryKey = this._map.keys().next().value;
      this._map.delete(firstMapEntryKey);
    }
  }

  public reset(): void {
    if (this._maxSize <= 0) return;

    this._map.clear();
  }

  public peek(key: K): V | null {
    if (this._maxSize <= 0) return null;

    const element: CacheElement<V> | undefined = this._map.get(key);

    return element?.value ?? null;
  }
}

An additional dependency has been added to the Optimizely client’s readyPromise promise resolution dependency array which resolves based on the success of initializing the VuidManager using localStorage.

Use authenticated datafile in secure environment

📘

Note

Authenticated datafiles are in beta. Contact your Customer Success Manager if you are interested in becoming an early user of authenticated datafiles as part of the beta secure environment feature.

You can fetch the Optimizely datafile from an authenticated endpoint using a server-side (only) Optimizely Feature Experimentation SDK. To use an authenticated datafile, download your Optimizely environment's access token from the Optimizely app at Settings>Environments. Select your secure environment, and copy the Datafile access token. The example below shows how to initialize the Optimizely client using an access token and sdk_key, enabling the client to fetch the authenticated datafile and complete initialization.

const optimizely = require('@optimizely/optimizely-sdk');

// fetch the datafile from an authenticated endpoint
const optimizelyClientInstance = optimizely.createInstance({
  sdkKey: '<YOUR_SDK_KEY>',
  datafileOptions: {
    datafileAccessToken: '<YOUR_DATAFILE_ACCESS_TOKEN>',
  },
});

Source files

The source code files containing the implementation for the JavaScript SDK are at index.ts

Updated 3 days ago