How to get type of string array

a!listType(type!Text)

I misunderstood that you wanted the type value (103) instead of an empty string array.  I like Stefan's answer then

Also for reference, if you want a quick way in your environment to see the type numbers in Appian (we use this in a COE/internal report), plug this into an empty interface.  Appian data types are ~1-300, CDTs begin at 500.

Note, never apply the try() (or any other undocumented function) in production, although it would be nice to have, it is not supported currently and may be removed at any time. 

a!richTextDisplayField(
  label: "Data Types",
  value: {
    a!forEach(
      items: 1+enumerate(1500),
      expression: {
        a!richTextItem(
          text: concat(
            fv!item,
            " - ",
            /* do not use try() in production! */
            try(typename(fv!item),"")
          )
        ),
        char(13)
      }
    )
  }
)

I misunderstood that you wanted the type value (103) instead of an empty string array.  I like Stefan's answer then

Also for reference, if you want a quick way in your environment to see the type numbers in Appian (we use this in a COE/internal report), plug this into an empty interface.  Appian data types are ~1-300, CDTs begin at 500.

Note, never apply the try() (or any other undocumented function) in production, although it would be nice to have, it is not supported currently and may be removed at any time. 

a!richTextDisplayField(
  label: "Data Types",
  value: {
    a!forEach(
      items: 1+enumerate(1500),
      expression: {
        a!richTextItem(
          text: concat(
            fv!item,
            " - ",
            /* do not use try() in production! */
            try(typename(fv!item),"")
          )
        ),
        char(13)
      }
    )
  }
)