ClearAll[setup]
SetAttributes[setup, HoldRest]
setup[x_, z_, numX_] := (numX = Length[x];
  Do[z[i] = StringLength[x[[i]]], {i, numX}])

g[x_List] := Module[
  {numX, z},
  setup[x, z, numX];
  Table[z[i], {i, numX}]
  ]