setupExperiment()

in src/amo/withExperiment.js [223:260]

• 22 lines of code
• 7 McCabe index (conditional complexity)

      setupExperiment(props) {
        const { _getVariant, dispatch, isUserExcluded, storedVariants } = props;

        // If the experiment is not enabled, we return a null variant.
        if (!this.isEnabled()) {
          return null;
        }

        // Always use the variant from the cookie, if it exists.
        let variant = this.readVariantFromCookie();

        if (!variant) {
          const variantFromStore = storedVariants[id];
          // Look for a variant in the Redux store.
          if (variantFromStore) {
            variant = variantFromStore;
          }
          // Otherwise if the user is to be excluded, use the NOT_IN_EXPERIMENT
          // variant.
          else if (isUserExcluded) {
            variant = NOT_IN_EXPERIMENT;
          } else {
            variant = _getVariant({ variants });
          }

          // Do we need to store the variant in the cookie?
          if (!this.cookieIncludesExperiment() && !variantFromStore) {
            // Store the variant in the Redux store for use during
            // `componentDidMount()` and only when the user does not yet have a
            // variant in a cookie. In this case, the `experiments` state would
            // be empty, which is a bit unusual as we normally have consistent
            // states.
            dispatch(storeExperimentVariant({ id, variant }));
          }
        }

        return variant;
      }