Mathematica Typing Effect

Question

Here is a Typing Effect in javascript.

I could only implement a very simple one:

DynamicModule[{s = ""},
 Dynamic[Refresh[
   If[Length[s] > 10, s = "", s = s <> "x"],
   TrackedSymbols :> {}, UpdateInterval -> 0.5]]]

How can I do that exactly the same?

Answer 1

Perhaps

typingEffect[str_String, secPerLetter_: 0.3] := 
 Dynamic[StringTake[str, 
   Clock[{0, StringLength@str, 1}, StringLength@str secPerLetter]]]

(thanks @SjoerdC.deVries)

So this gives an animation

typingEffect["hello my dear"]

Other effects can be implemented with the same idea, such as

typingEffect2[str_String] := 
 Row@MapIndexed[
   Style[#, 
      FontColor->Dynamic@ColorData["Rainbow"][
       Mod[(First@#2 - 0.5)/StringLength@str + Clock[], 1]]] &, 
   Characters@str]

Answer 2

Implementation with ScheduledTask. When the Type button is pushed, a scheduled task is started that increases the display length of the temporary string temp. It can be paused (Stop) and continued (Type again).

text = StringTake[ExampleData[{"Text", "LoremIpsum"}], 120]

temp = ""; task = None; n = 0;
Row@{Button["Type", If[task =!= None, RemoveScheduledTask@task]; 
   task = RunScheduledTask[
     If[n > StringLength@text, RemoveScheduledTask@task; n = 0, 
      temp = StringTake[text, n++]], 0.01]],
  Button["Stop", If[task =!= None, RemoveScheduledTask@task]]}
Dynamic@temp