Optional addBuilds an object that encapsulates the state of all feature flags for a given context. This includes the flag values and also metadata that can be used on the front end. This method does not send analytics events back to LaunchDarkly.
The most common use case for this method is to bootstrap a set of client-side
feature flags from a back-end service. Call the toJSON() method of the returned object
to convert it to the data structure used by the client-side SDK.
The context requesting the feature flags.
Optional options: LDFlagsStateOptionsOptional LDFlagsStateOptions to determine how the state is computed.
Optional Optional callback: ((err, res) => void)A Node-style callback to receive the result (as an LDFlagsState). If omitted, you will receive a Promise instead.
Optional
If you provided a callback, then nothing. Otherwise, a Promise which will be resolved with the result as an LDFlagsState.
Determines the boolean variation of a feature flag for a context.
If the flag variation does not have a boolean value, defaultValue is returned.
The unique key of the feature flag.
The context requesting the flag. The client will generate an analytics event to register this context with LaunchDarkly if the context does not already exist.
The default value of the flag, to be used if the value is not available from LaunchDarkly.
A Promise which will be resolved with the result value.
Determines the boolean variation of a feature flag for a context, along with information about how it was calculated.
The reason property of the result will also be included in analytics events, if you are
capturing detailed event data for this flag.
If the flag variation does not have a boolean value, defaultValue is returned. The reason will
indicate an error of the type WRONG_KIND in this case.
For more information, see the SDK reference guide.
The unique key of the feature flag.
The context requesting the flag. The client will generate an analytics event to register this context with LaunchDarkly if the context does not already exist.
The default value of the flag, to be used if the value is not available from LaunchDarkly.
Flushes all pending analytics events.
Normally, batches of events are delivered in the background at intervals determined by the
flushInterval property of LDOptions. Calling flush() triggers an immediate
delivery. However, like Node I/O in general, this is still an asynchronous operation so you
must still use Promise chaining, a callback, or async/await to detect when it has finished
or failed.
Optional callback: ((err, res) => void)A function which will be called when the flush completes (meaning that all pending events have been delivered to LaunchDarkly). If omitted, you will receive a Promise instead.
Optional
If you provided a callback, then nothing. Otherwise, a Promise which resolves once flushing is finished. Note that the Promise will be rejected if the HTTP request fails, so be sure to attach a rejection handler to it.
Identifies a context to LaunchDarkly.
This simply creates an analytics event that will transmit the given user properties to LaunchDarkly, so that the context will be visible on your dashboard even if you have not evaluated any flags for that user. It has no other effect.
If the context is omitted or has no key, the client will log a warning and will not send an event.
The context properties. Must contain at least the key property.
Tests whether the client has completed initialization.
If this returns false, it means that the client has not yet successfully connected to LaunchDarkly. It might still be in the process of starting up, or it might be attempting to reconnect after an unsuccessful attempt, or it might have received an unrecoverable error (such as an invalid SDK key) and given up.
True if the client has successfully initialized.
Tests whether the client is configured in offline mode.
True if the offline property is true in your LDOptions.
Determines the variation of a feature flag for a context.
This version may be favored in TypeScript versus variation because it returns
an unknown type instead of any. unknown will require a cast before usage.
The unique key of the feature flag.
The context requesting the flag. The client will generate an analytics event to register this context with LaunchDarkly if the context does not already exist.
The default value of the flag, to be used if the value is not available from LaunchDarkly.
A Promise which will be resolved with the result value.
Determines the variation of a feature flag for a context, along with information about how it was calculated.
The reason property of the result will also be included in analytics events, if you are
capturing detailed event data for this flag.
This version may be favored in TypeScript versus variation because it returns
an unknown type instead of any. unknown will require a cast before usage.
For more information, see the SDK reference guide.
The unique key of the feature flag.
The context requesting the flag. The client will generate an analytics event to register this context with LaunchDarkly if the context does not already exist.
The default value of the flag, to be used if the value is not available from LaunchDarkly.
If you provided a callback, then nothing. Otherwise, a Promise which will be resolved with
the result (as an
Returns the migration stage of the migration feature flag for the given evaluation context.
If the evaluated value of the flag cannot be converted to an LDMigrationStage, then the default value will be returned and error will be logged.
The unique key of the feature flag.
The context requesting the flag. The client will generate an analytics event to register this context with LaunchDarkly if the context does not already exist.
The default value of the flag, to be used if the value is not available from LaunchDarkly.
A Promise which will be resolved with the result (as anLDMigrationVariation).
Determines the numeric variation of a feature flag for a context.
If the flag variation does not have a numeric value, defaultValue is returned.
The unique key of the feature flag.
The context requesting the flag. The client will generate an analytics event to register this context with LaunchDarkly if the context does not already exist.
The default value of the flag, to be used if the value is not available from LaunchDarkly.
A Promise which will be resolved with the result value.
Determines the numeric variation of a feature flag for a context, along with information about how it was calculated.
The reason property of the result will also be included in analytics events, if you are
capturing detailed event data for this flag.
If the flag variation does not have a numeric value, defaultValue is returned. The reason will
indicate an error of the type WRONG_KIND in this case.
For more information, see the SDK reference guide.
The unique key of the feature flag.
The context requesting the flag. The client will generate an analytics event to register this context with LaunchDarkly if the context does not already exist.
The default value of the flag, to be used if the value is not available from LaunchDarkly.
Computes an HMAC signature of a context signed with the client's SDK key.
For more information, see the JavaScript SDK Reference Guide on Secure mode.
The context properties.
The hash string.
Determines the string variation of a feature flag for a context.
If the flag variation does not have a string value, defaultValue is returned.
The unique key of the feature flag.
The context requesting the flag. The client will generate an analytics event to register this context with LaunchDarkly if the context does not already exist.
The default value of the flag, to be used if the value is not available from LaunchDarkly.
A Promise which will be resolved with the result value.
Determines the string variation of a feature flag for a context, along with information about how it was calculated.
The reason property of the result will also be included in analytics events, if you are
capturing detailed event data for this flag.
If the flag variation does not have a string value, defaultValue is returned. The reason will
indicate an error of the type WRONG_KIND in this case.
For more information, see the SDK reference guide.
The unique key of the feature flag.
The context requesting the flag. The client will generate an analytics event to register this context with LaunchDarkly if the context does not already exist.
The default value of the flag, to be used if the value is not available from LaunchDarkly.
Tracks that a context performed an event.
LaunchDarkly automatically tracks pageviews and clicks that are specified in the Metrics section of the dashboard. This can be used to track custom metrics (goals) or other events that do not currently have metrics.
Note that event delivery is asynchronous, so the event may not actually be sent until later; see flush.
If the context is omitted or has no key, the client will log a warning and will not send an event.
The name of the event, which may correspond to a metric in Experimentation.
The context to track.
Optional data: anyOptional additional information to associate with the event.
Optional Optional metricValue: numberA numeric value used by the LaunchDarkly experimentation feature in numeric custom metrics. Can be omitted if this event is used by only non-numeric metrics. This field will also be returned as part of the custom event for Data Export.
Optional Track the details of a migration.
Event containing information about the migration operation.
Determines the variation of a feature flag for a context.
The unique key of the feature flag.
The context requesting the flag. The client will generate an analytics event to register this context with LaunchDarkly if the context does not already exist.
The default value of the flag, to be used if the value is not available from LaunchDarkly.
Optional callback: ((err, res) => void)A Node-style callback to receive the result value. If omitted, you will receive a Promise instead.
Optional
If you provided a callback, then nothing. Otherwise, a Promise which will be resolved with the result value.
Determines the variation of a feature flag for a context, along with information about how it was calculated.
The reason property of the result will also be included in analytics events, if you are
capturing detailed event data for this flag.
For more information, see the SDK reference guide.
The unique key of the feature flag.
The context requesting the flag. The client will generate an analytics event to register this context with LaunchDarkly if the context does not already exist.
The default value of the flag, to be used if the value is not available from LaunchDarkly.
Optional callback: ((err, res) => void)A Node-style callback to receive the result (as an LDEvaluationDetail). If omitted, you will receive a Promise instead.
Optional
If you provided a callback, then nothing. Otherwise, a Promise which will be resolved with the result (as anLDEvaluationDetail).
Returns a Promise that tracks the client's initialization state.
The Promise will be resolved if the client successfully initializes, or rejected if client
initialization has failed unrecoverably (for instance, if it detects that the SDK key is
invalid). Keep in mind that unhandled Promise rejections can be fatal in Node, so if you call
this method, be sure to attach a rejection handler to it (or, if using async/await, a catch
block).
Note that you can also use event listeners (on) for the same purpose: the event
"ready" indicates success, and "failed" indicates failure.
This method takes an optional parameters which include a timeout. The timeout controls how long a specific call to waitForInitialization will wait before rejecting its promise. If a subsequent call is made to waitForInitialization with a timeout, then it will again wait up to that maximum time.
Regardless of whether you continue to wait, the SDK will still retry all connection failures indefinitely unless it gets an unrecoverable error as described above.
Waiting indefinitely, or depending only on the "ready" or "failed" events can result in an application waiting indefinitely. It is recommended to use a timeout which is reasonable for your application.
Optional options: LDWaitForInitializationOptionsOptions which control the behavior of waitForInitialization.
Optional A Promise that will be resolved if the client initializes successfully, or rejected if it fails. If successful, the result is the same client object. It is not recommended to use the returned client object. It will be removed in a future version.
This example shows use of Promise chaining methods for specifying handlers:
client.waitForInitialization({timeoutSeconds: 10}).then(() => {
// do whatever is appropriate if initialization has succeeded
}).catch(err => {
// do whatever is appropriate if initialization has failed or timed out
})
This example shows use of async/await syntax for specifying handlers:
try {
await client.waitForInitialization({timeoutSeconds: 10});
// do whatever is appropriate if initialization has succeeded
} catch (err) {
// do whatever is appropriate if initialization has failed or timed out
}
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The LaunchDarkly SDK client object.
Create this object with init. Applications should configure the client at startup time and continue to use it throughout the lifetime of the application, rather than creating instances on the fly.