Optimize Server-side Experiments gtag.js

Question

The docs for Google optimize server side events are written for analytics.js is there a way to do the same thing using gtag.js? https://developers.google.com/optimize/devguides/experiments

ga('set', 'exp', `${experimentId}.${variationId}`);
ga('send', 'pageview');

something along the lines of:

gtag('event', '???', {
???: `${experimentId}.${variantPosition}`,
});

Answer 1

The syntax and docs link has been updated:

    gtag('event', 'experiment_impression', {​
      'experiment_id': '$experimentId',
      'variant_id': '$experimentId.$variantid',
      'send_to': 'GA_MEASUREMENT_ID',
    });

Source: https://developers.google.com/optimize/devguides/experiments?technology=ga4#add-ga-tracking-code-to-variants

Answer 2

this syntax should work:

gtag('set', {'experiments': [{'id': 'exp_id', 'variant': '1'}]});

source: https://support.google.com/optimize/thread/36142685/is-there-a-way-to-implement-the-server-side-experiments-with-a-gtag-instead-of-ga-tracking-code?hl=en