Writing properly escaped strings to a file

I have to write a properly (as in JSON or Javascript) escaped string to a file.

My minimal example is

documentclass{standalone}

begingroup
catcode`<=1 catcode`>=2
catcode`{=12 catcode`}=12
gdefwbgroup<{>
gdefwegroup<}>
endgroup

defmytitle{This is a "title" for me}

begin{document}
newwritejsonwrite
immediateopenoutjsonwrite=file.json
immediatewritejsonwrite{wbgroup}
immediatewritejsonwrite{  title: "mytitle"}
immediatewritejsonwrite{wegroup}
end{document}

What I get is a file.json with

{
 title: "This is a "title" for me"
}

whereas what I need is the internal quotes escaped as in

{
 title: "This is a "title" for me"
}

I have the suggestion Escaping quotes when writing to a file but if I do this

documentclass{standalone}

begingroup
catcode`<=1 catcode`>=2
catcode`{=12 catcode`}=12
gdefwbgroup<{>
gdefwegroup<}>
endgroup

usepackage[T1]{fontenc}
usepackage{expl3}
ExplSyntaxOn
newcommand{myescapestring}[1]{
  tl_set:Nn l_tmpa_tl {#1}
  regex_replace_all:nnN {"} {u{c_backslash_str}"} l_tmpa_tl
  tl_use:N l_tmpa_tl
}
ExplSyntaxOff

defmytitle{This is a "title" for me}

begin{document}
newwritejsonwrite
immediateopenoutjsonwrite=file.json
immediatewritejsonwrite{wbgroup}
immediatewritejsonwrite{  title: "myescapestringmytitle"}
immediatewritejsonwrite{wegroup}
end{document}

I get an even much worse result, namely

{
 title: "tl_set:Nn {This is a "title" for me}regex_replace_all:nnN {"}{unhbox voidb@x bgroup let unhbox voidb@x setbox @tempboxa hbox {c_backslash_strglobal mathchardef accent@spacefactor spacefactor }let begingroup endgroup relax let ignorespaces relax accent 8 c_backslash_stregroup spacefactor accent@spacefactor "}"
}

I am stuck with PDFLaTeX and cannot use LUATex, since I am using many features of PDFLaTeX in other parts of my original document.

So essentially I am looking for a stringEscape function for Javascript in PDFTeX.

documentclass{article}

ExplSyntaxOn
NewDocumentCommand{jsonwrite}{mmmm}
 {% #1 = file name,
  % #2 = initial part
  % #3 = middle part
  % #4 = final part
  nkiad_jsonwrite:nnnn { #1 } { #2 } { #3 } { #4 }
 }

iow_new:N g__nkiad_jsonwrite_iow
tl_new:N l__nkiad_jsonwrite_item_tl

cs_generate_variant:Nn iow_now:Nn { NV }

cs_new_protected:Nn nkiad_jsonwrite:nnnn
 {
  iow_open:Nn g__nkiad_jsonwrite_iow { #1 }
  iow_now:Nx g__nkiad_jsonwrite_iow { c_left_brace_str }
  tl_set:Nx l__nkiad_jsonwrite_item_tl { #3 }
  regex_replace_all:nnN { " } { cO " } l__nkiad_jsonwrite_item_tl
  iow_now:Nx g__nkiad_jsonwrite_iow
   {
    #2 % initial part
    l__nkiad_jsonwrite_item_tl % middle part
    #4 % final part
   }
  iow_now:Nx g__nkiad_jsonwrite_iow { c_right_brace_str }
  iow_close:N g__nkiad_jsonwrite_iow
 }
ExplSyntaxOff

defmytitle{This is a "title" for me}

begin{document}

jsonwrite{jobname.json}{  title: "}{mytitle}{"}

end{document}