Send a form impression event to GA4 using gtag.js API.

send-form-impression-ga4-using-gtag.js

(function() {
    if (typeof gtag === 'undefined') {
          console.log('[GA4] gtag is undefined.');
          return;
    }
    const formElts = document.querySelectorAll('form');
    let formName = '(not set)';
    // If no forms, bail.
    if (formElts.length === 0) return;
    [...formElts].map((f) => {
        console.log(`Got a form: ${f}`);
        try {
            formName = f.dataset.formName || f.getAttribute('id') || '(not set)';
            console.log(`[GA4] Sending impression for form: ${formName}`);
			// Changed the event name from FormImpression and parameter
			// from FormName for MI compliance 18 June 2021.
			gtag("event", "form_impression", { 
          		'form_id': "'" + formName + "'",
            });
        } catch (e) {
              console.log("[GA4] Something wrong happened when setting up event handling for forms.");
        }
    });
})()