>Where did you get that syntax from? There is no moment function that takes a date and a string - it's either a date OR a string (with an optional second string to inform on the format of the date in the first string). IAC all you need is :

$scope.currentData.age = moment().diff(newValue,"years");

Read the docs: https://momentjs.com/docs/

I don't know who wrote that syntax, but I did figure out exactly that on my own and I did read the docs (that's how I figured the needed change).