Migration

To randomize strings as such (and also apply the same to numeric values), create 2 helper rules:

rule!chris_test_randomize_numeric(numeric)

tointeger(
  joinarray(
    a!forEach(
      items: 1+enumerate(len(ri!numeric)),
      expression: {
        a!localVariables(
          local!random: tointeger(rand()*9-1)+1,
          if(
            and(
              fv!isFirst,
              local!random=0
            ),
            1, /* change to 1 to maintain length */
            local!random
          )
        )
      }
    )
  )
)

rule!chris_test_randomize_string(text)

a!localVariables(
  local!alpha: "abcdefghijklmnopqrstuvwxyz",
  joinarray(
    a!forEach(
      items: code(ri!text),
      expression: {
        a!localVariables(
          local!random: index(local!alpha,tointeger(rand()*len(local!alpha)-1)+1,null),
          if(
            fv!item<97,
            upper(local!random),
            local!random
          )
        )
      }
    )
  )
)

Then call your new rules when converting your CDT:

a!localVariables(
  local!data: {
    a!map(id: 1, firstName: "John", lastName: "Doe", salary: 50000),
    a!map(id: 2, firstName: "Jane", lastName: "Doe", salary: 55000),
    a!map(id: 3, firstName: "Timothy", lastName: "McDonald", salary: 45000)
  },

  a!forEach(
    items: local!data,
    expression: a!map(
      id: fv!item.id,
      firstName: rule!chris_test_randomize_string(text: fv!item.firstName),
      lastName: rule!chris_test_randomize_string(text: fv!item.lastName),
      salary: rule!chris_test_randomize_numeric(numeric: fv!item.salary)
    )
  )
)