Decide methods for the JavaScript (Browser) SDK prior to v6
Use the decide methods to return feature flag decisions for a user. Each decision includes whether the flag is enabled and which variation the user receives.
Decide
Returns a decision for a specific feature flag and user.
Minimum SDK version – v4.5+
Description
The decide method handles the variation decision for an individual experiment. It returns a decision result for a flag key for a user in an OptimizelyDecision object and contains the data required to deliver the flag rule.
This method ensures that Feature Experimentation properly buckets the user in experiment analytics, and you should use it if there is no need for pre-rendering decisions.
Decide is a method of the UserContext object. See OptimizelyUserContext for details.
See the OptimizelyDecision documentation for details of the returned decision object.
Key features
- Single experiment decision – Returns the variation for a specific experiment.
- Bucketing in results – Ensures Feature Experimentation records the user in the experiment results page for proper analysis.
- Complement to decide all method – If you use the decide all method to pre-fetch variations, you should also call the decide method for each experiment that the user interacts with. This dual approach guarantees that Feature Experimentation accurately tracks the user's participation and that the correct variation is served through caching.
- CMAB support – For CMAB experiments, decisions are automatically cached to reduce latency. The cache is invalidated when CMAB attributes change or TTL expires. Use CMAB-specific decide options (IGNORE_CMAB_CACHE, INVALIDATE_USER_CMAB_CACHE, and RESET_CMAB_CACHE) to override default caching behavior. See the following CMAB cache control information.
Parameters
The following table describes parameters for the decide method:
Parameter | Type | Description |
|---|---|---|
flagKey | String | The key of the feature flag |
options (optional) | Array | Array of OptimizelyDecideOption enums. |
Returns
The decide method returns an OptimizelyDecision object.
If the method encounters a critical error (SDK not ready, invalid flag key, and so on), then it returns a decision with a null variationKey field and populates the reasons field with error messages (regardless of the OptimizelyDecideOption.INCLUDE_REASONS option).
Example decide
// Create the user and decide which flag rule and variation they bucket into
const attributes = {
logged_in: true
};
const user = optimizely.createUserContext('user123', attributes);
const decision = user.decide('product_sort');
// The variation key. If null, decision failed with a critical error
const variationKey = decision['variationKey'];
if (variationKey === null) {
console.log(' decision error: ', decision['reasons']);
}
// The flag enabled state
const enabled = decision['enabled'];
// String variable value
const value = decision.variables['sort_method'];
// All variable values
const allVarValues = decision['variables'];
// Flag decision reasons
const reasons = decision['reasons'];
// User for which the decision was made
const userContext = decision['userContext'];Side effect
Invokes the decision notification listener if this listener is enabled.
Decide all
Returns decisions for all active (unarchived) flags for a user.
Minimum SDK version – v4.5+
Description
Use the decide all method to retrieve decisions for all active flags before rendering content. This is particularly useful when you need to serve the correct cached version of your page or component based on the user's variation. For example when using an edge worker or cloud function.
Key features
- Pre-rendering decision – Lets you know all variation assignments ahead of time.
- Cache control – Lets you serve the correct cached content based on the user's pre-determined variations.
- Delay experiment tracking – Use DISABLE_DECISION_EVENT to prevent the SDK from recording a decision before the user sees the feature. This ensures that participation is only tracked when the experience is delivered.
- CMAB support – For CMAB experiments (SDK v5.2.0+), decisions are automatically cached to reduce latency. The cache is invalidated when CMAB attributes change or TTL expires. Use CMAB-specific decide options (ignoreCmabCache, invalidateUserCmabCache, resetCmabCache) to override default caching behavior. See CMAB cache control.
Parameters
The following table describes parameters for the decide all method:
Parameter | Type | Description |
|---|---|---|
options (optional) | Array | Array of OptimizelyDecideOption enums. |
Returns
Returns a map of OptimizelyDecisions.
If the method fails for all flags (for example, the SDK is not ready or the user context is invalid), then it returns an empty map. If the method detects an error for a specific flag, it returns error messages in the reasons field of the decision for that flag.
Example decideAll
const attributes = {
logged_in: true
};
const user = optimizely.createUserContext('user123', attributes);
// Make decisions for all active (unarchived) flags in the project for a user
let decisions = user.decideAll();
// Or only for enabled flags
decisions = user.decideAll([OptimizelyDecideOption.ENABLED_FLAGS_ONLY]);
const flagKeys = Object.keys(decisions);
const decisionForFlag1 = decisions['flag_1'];Side effect
Invokes the decision notification listener for each decision if this listener is enabled.
Decide for keys
Returns a map of flag decisions for specified flag keys.
Minimum SDK version – v4.5+
Description
Returns a map of decisions for the specified flag keys.
Parameters
The following table describes parameters for the decide for keys method:
Parameter | Type | Description |
|---|---|---|
keys | Array | Array of string flag keys. |
options (optional) | Array | Array of OptimizelyDecideOption enums. |
Returns
Returns a map of OptimizelyDecisions. For information, see OptimizelyDecision.
If the method fails for all flags (for example, the SDK is not ready or the user context is invalid), then it returns an empty map. If the method detects an error for a specific flag, it returns error messages in the reasons field of the decision for that flag.
Example decideForKeys
// Make a decisions for specific enabled flags
const keys = ['flag_1', 'flag_2'];
const decisions = user.decideForKeys(keys);
const decision1 = decisions['flag_1'];
const decision2 = decisions['flag_2'];Side effect
Invokes the decide notification listener for each decision if this listener is enabled.
OptimizelyDecideOption
The following table lists the OptimizelyDecideOption enum with an explanation what happens if you set them. In addition to setting these options individually for a decide method, you can also set them as global defaults when you instantiate the Optimizely client. See Initialize JavaScript SDK.
The following code sample shows how to implement the OptimizelyDecideOption as a global default and locally in a decide method call.
import { createInstance, OptimizelyDecideOption } from '@optimizely/optimizely-sdk';
// Set global default decide options when initializing the client
const optimizely = createInstance({
sdkKey: 'YOUR_SDK_KEY', // Replace with your SDK key
defaultDecideOptions: [OptimizelyDecideOption.DISABLE_DECISION_EVENT],
});
if (optimizely) {
optimizely.onReady().then(({ success, reason }) => {
if (!success) {
throw new Error(reason);
}
const user = optimizely.createUserContext('user123');
if (!user) {
throw new Error('failed to create user context');
}
// Set additional options in a decide call
const decisionResults = user.decideAll(
[
OptimizelyDecideOption.ENABLED_FLAGS_ONLY,
OptimizelyDecideOption.IGNORE_USER_PROFILE_SERVICE,
]
);
console.log(decisionResults);
}).catch((err) => {
// Handle error
});
} else {
// Handle instantiation error
}Best practices
- Early and late invocation
- Use the decide all method early in your application's rendering process to load the correct cached content. For example, on the CDN with an Edge SDK.
- Use the decide method at the point of user interaction or when you must ensure Feature Experimentation records the decision in your experiment analytics.
- Combining methods – When using the decide and decide all methods, always pair the decide all method with the decide method for each experiment the user encounters. This prevents discrepancies between served content and analytics data.
- Parameter management – Ensure you use the DISABLE_DECISION_EVENT option with the decide all method to avoid premature bucketing, then use the decide method to handle the decision event when the user experiences the content.
Source files
The language and platform source files containing the implementation for the JavaScript (Browser) SDK are available on GitHub.