Get Feature Variable

Evaluates the specified feature variable of a specific variable type and returns its value.

This method is used to evaluate and return a feature variable. Multiple versions of this method are available and are named according to the data type they return:

• Generic (only v3.3+)
• Boolean
• Double
• Integer
• String
• JSON

This method takes into account the user attributes passed in, to determine if the user is part of the audience that qualifies for the experiment.

Generic

Starting in v3.3.0 of the SDK, you can use the generic feature variable accessor. This can return a number, boolean, or string depending on the variable's defined type.

function getFeatureVariable(featureKey, variableKey, userId, attributes)

Boolean

Returns the value of the specified Boolean variable.

function getFeatureVariableBoolean(featureKey, variableKey, userId, attributes)

Double

Returns the value of the specified double variable.

function getFeatureVariableDouble(featureKey, variableKey, userId, attributes)

Integer

Returns the value of the specified integer variable.

function getFeatureVariableInteger(featureKey, variableKey, userId, attributes)

String

Returns the value of the specified string variable.

function getFeatureVariableString(featureKey, variableKey, userId, attributes)

JSON

Returns the value of the specified JSON variable.

function getFeatureVariableJson(featureKey, variableKey, userId, attributes)

Version

SDK v3.0, v3.1, v3.3

Description

Each of the Get Feature Variable methods follows the same logic as Is Feature Enabled:

1. Evaluate any feature tests running for a user.
2. Check the default configuration on a rollout.

The default value is returned if neither of these are applicable for the specified user, or if the user is in a variation where the feature is disabled.

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Important

Unlike Is Feature Enabled, the Get Feature Variable methods do not trigger an impression event. This means that if you are running a feature test, events will not be counted until you call Is Feature Enabled. If you do not call Is Feature Enabled, you will not see any visitors on your results page.

Parameters

Required and optional parameters are listed below.

Returns

@return object | n object | n{string | number | boolean | object | null} The value of the variable, or null if the feature key is invalid, the variable key is invalid, or there is a mismatch with the type of the variable.

Example

var attributes = {
  device: 'iPhone',
  lifetime: 24738388,
  is_logged_in: true,
};

var featureVariableValue = optimizelyClient.getFeatureVariableDouble('my_feature_key', 'double_variable_key', 'user_123', attributes);

// or in v3.3+ you can use the untyped variable accessor, which will return a number if the variable you defined in the Optimizely Dashboard is of type double
var featureVariableValue = optimizelyClient.getFeatureVariable('my_feature_key', 'double_variable_key', 'user_123', attributes);

See also

Is Feature Enabled

Side effects

In SDKs v3.1 and later: Invokes the DECISION notification listener if this listener is enabled.

Source files

The language/platform source files containing the implementation for JavaScript are available on GitHub.