Zapier | Check if field exists or has value, then change the output value if it does or doesn't

zapier-code-check-field-value-exists.js

// this is wrapped in an `async` function
// you can use await throughout the function

// just in case, initially we set the output of this object to be false
output = {clientIdResult: false};

// get the variable from the inputData we added to this Action
var clientid = inputData.clientId;

// check if the variable had data
if(clientid) {
	// if it did, output this content with the variable
	output['clientIdResult'] = 'https://analytics.google.com/analytics/web/#/report/visitors-user-activity/a7891781w50370125p50966238/_u.date00=19990101&_u.date01=29990101&_r.userId=' + clientid;
}
// otherwise it didn't have any data
else {
	// so we specify a different output for the value
	output['clientIdResult'] = 'NA'; 
}

Screenshot: https://i.imgur.com/bHhv9iA.png