F# html and javascript generator

clorets.fs

open System

type Html =
  | Tag of string * Html list
  | Attribute of string * string
  | Content of string
  override __.ToString() = 
    match __ with
    | Tag (tag,htmls) ->
      let mutable attributes = ""
      let mutable innerHtml = ""
      for html in htmls do
        let str = string html
        match html with
        | Attribute (key,value) -> 
          attributes <- sprintf "%s %s" attributes str
        | _ -> 
          innerHtml <- sprintf "%s\n%s" innerHtml str
      sprintf "<%s%s>%s\n</%s>" tag attributes innerHtml tag
    | Attribute(key,value) -> sprintf @"%s=""%s""" key value
    | Content content -> content

let tag tag htmls = Tag(tag,htmls) 

let html = tag "html" 
let body = tag "body"
let head = tag "head"
let h1 = tag "h1"
let p = tag "p"

let attr key value = Attribute(key,value)
let id = attr "id"
let typ = attr "type"

let (=<) tag content = tag [Content content]
let (-<) tag html htmls = tag (html::htmls)
let s str = Content str

let script =
  tag "script" -< typ "text/javascript"

module Doc =
  let write str = 
    (string str).Replace("<",@"""<").Replace(">",@">""")
    |> sprintf @"document.write(%s);"
  
  let byId id = 
    sprintf @"document.getElementById(""%s"")" id

let writeFile file html =
  let html = string html
  IO.File.WriteAllText(file,html)
  Diagnostics.Process.Start(@"C:\chrome.lnk",file)
  |> ignore

let fn0 name body =
  sprintf "function %s(){\n%s;}\n" name body

html [
  head [
    script [
      fn0 "displayDate" <| Doc.byId "demo" + ".innerHtml=Date()"
    ]
  ]
  body [
    h1 =< "My First Web Page"
    p [
      id "demo"
      s"aiueo"
    ]
    script =< Doc.write (p =< "+ Date() +") 
    script =< Doc.byId "demo" + ".innerHTML=Date()"
  ]
]
|> writeFile @"C:\fsharp\clorets\pages\index.html"