The ff-set attribute allows an end user to set a value when clicking a element, typically used with <a> and <button> elements. Important: If the target value does not exist, an error will occur causing other aspects of your web page not to work. A value exists if it is in firebase or in an element like <input>.
Click the above links and notice the value change in the Firebase emulator. Firebase's security prevents myValue from being set to a non-number.
Click the above buttons and notice the value change in the Firebase emulator. Firebase's security can prevents setText from being set to anything but alpha or beta.