Check if user attribute is set

Check if a User Attribute already exists via the webchat SDK.
A user exists if it has been whitelisted, and has been set at least one time.

Call will return a promise:

window.ClustaarWebchat.isSet('city').then(function(exists){
  // "exists" is a boolean: true if the attribute is whitelisted, and has been set
  console.log(exists)
});