useDecision hook for the React SDK

5 min

Minimum SDK version – v2.5+

useDecision hook

Retrieves the decision result for a flag key, optionally auto-updating that decision based on underlying user, datafile, or forced decision changes.

Arguments

Argument	Type	Description
`flagKey `(required)	String	The key of the feature flag
`options `(optional)	Object	Includes the following: `autoUpdate` (boolean) - If true, this hook updates the flag decision in response to datafile or user changes. Default: `false`. `timeout` (number) - Client timeout as described in the [`OptimizelyProvider`](https://docs.developers.optimizely.com/feature-experimentation/docs/optimizelyprovider-react-prior-to-v4) documentation. Overrides any timeout set on the ancestor `OptimizelyProvider`. `decideOptions` (`OptimizelyDecideOption`) - Array of `OptimizelyDecideOption` enums. See [OptimizelyDecideOption](#optimizelydecideoption).
`overrides `(optional)	Object	Includes the following: `overrideUserId` (string) - Override the userId to be used to obtain the decision result for this hook. `overrideAttributes` (optimizely.UserAttributes) – Override the user attributes to be used to obtain the decision result for this hook.

Returns

Returns an array with the following:

Key	Type	Description
`decision`	[OptimizelyDecision](https://docs.developers.optimizely.com/feature-experimentation/docs/optimizelydecision-react-prior-to-v4)	Decision result for the flag key.
`clientReady`	Boolean	Indicates whether the `ReactSDKClient` instance is ready.
`didTimeout`	Boolean	Indicates whether the `ReactSDKClient` instance became ready within the allowed timeout range. `clientReady` can be `true` even if `didTimeout` is also `true`. This indicates that the client became ready after the timeout period.

Example useDecision

import { useEffect } from 'react';
import { useDecision } from '@optimizely/react-sdk';

function LoginComponent() {
  const [decision, clientReady] = useDecision(
    'flag1',
    { autoUpdate: true },
    {
      /* (Optional) User overrides */
    }
  );
  useEffect(() => {
    document.title = decision.enabled ? 'New Feature flag' : 'Old Feature flag';
  }, [decision]);

  return (
    <p>
      <a href={decision.variationKey === 'login1' ? '/login' : '/login2'}>Click to login</a>
    </p>
  );
}

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 the React SDK.

OptimizelyDecideOption enum	If set
OptimizelyDecideOption.DISABLE_DECISION_EVENT	Prevents the SDK from dispatching an impression event when serving a variation. This disables decision tracking on the Optimizely Experiment Results page and the decision notification listener.
OptimizelyDecideOption.ENABLED_FLAGS_ONLY	Returns decisions only for flags that are currently enabled. Used with the decide all method and decide for keys method. When this option is not set, the Android SDK returns all decisions regardless of whether the flag is enabled.
OptimizelyDecideOption.IGNORE_USER_PROFILE_SERVICE	Bypasses the user profile service (both lookup and save) for the decision. When this option is not set, user profile service overrides audience targeting, traffic allocation, and experiment mutual exclusion groups.
OptimizelyDecideOption.INCLUDE_REASONS	Adds log messages to the reasons field of the decision. Critical errors are always returned, even if this option is not set.
OptimizelyDecideOption.EXCLUDE_VARIABLES	Excludes flag variable values from the decision result. Use this option to minimize the returned decision by skipping large JSON variables.
OptimizelyDecideOption.IGNORE_CMAB_CACHE	Bypasses the CMAB cache and fetches a fresh decision from the CMAB service. Use when you need real-time decisions that reflect the latest context.
OptimizelyDecideOption.INVALIDATE_USER_CMAB_CACHE	Removes the cached CMAB decision for this user and experiment before making the decision. Use when user context has changed significantly and you want to ensure a fresh decision.
OptimizelyDecideOption.RESET_CMAB_CACHE	Clears all entries from the CMAB cache before making the decision. Use sparingly for testing or cache corruption scenarios.

The following example shows how you can set options individually on the useDecision hook, or as global defaults when you instantiate the Optimizely client. See Initialize React SDK.

import { useEffect } from 'react';
import {
  createInstance,
  OptimizelyProvider,
  useDecision,
  OptimizelyDecideOption,
} from '@optimizely/react-sdk';

// Instantiate an Optimizely client
const optimizelyClient = createInstance({
  sdkKey: 'Your_SDK_Key', // Replace with your SDK key
  defaultDecideOptions: [OptimizelyDecideOption.DISABLE_DECISION_EVENT],
});

function LoginComponent() {
  const [decision, clientReady] = useDecision(
    'flag1',
    {
      autoUpdate: true,
      decideOptions: [
        OptimizelyDecideOption.ENABLED_FLAGS_ONLY,
        OptimizelyDecideOption.IGNORE_USER_PROFILE_SERVICE,
      ],
    },
    {
      /* (Optional) User overrides */
    }
  );
  useEffect(() => {
    document.title = decision.enabled ? 'New Feature flag' : 'Old Feature flag';
  }, [decision]);

  return (
    <p>
      <a href={decision.variationKey === 'login1' ? '/login' : '/login2'}>Click to login</a>
    </p>
  );
}

function App() {
  return (
    <OptimizelyProvider optimizely={optimizelyClient} user={{ id: 'user123' }}>
      <LoginComponent />
    </OptimizelyProvider>
  );
}