Mehrere Stylesheets nutzen / wechseln

Um mehrere externe Stylesheets zu benutzen, bin man zuerst die verschiedenen CSS-Dateien im -Bereich der Seite ein:

<link rel="stylesheet" type="text/css" href="style/ff.css" title="small" />

<link rel="alternate stylesheet" type="text/css" href="style/big.css" title="big" />

Nun bindet man folgendes Javascript in die Seite ein.

function set_active_sheet(title) {

  var i, a, main;

  for(i=0; (a = document.getElementsByTagName("link")[i]); i++) {

    if(a.getAttribute("rel").indexOf("style") != -1 && a.getAttribute("title")) {

      a.disabled = true;

      if(a.getAttribute("title") == title) a.disabled = false;

    }

  }

}



function get_active_sheet() {

  var i, a;

  for(i=0; (a = document.getElementsByTagName("link")[i]); i++) {

    if(a.getAttribute("rel").indexOf("style") != -1 && a.getAttribute("title") && !a.disabled) return a.getAttribute("title");

  }

  return null;

}



function get_preferred_sheet() {

  var i, a;

  for(i=0; (a = document.getElementsByTagName("link")[i]); i++) {

    if(a.getAttribute("rel").indexOf("style") != -1

       && a.getAttribute("rel").indexOf("alt") == -1

       && a.getAttribute("title")

       ) return a.getAttribute("title");

  }

  return null;

}



function create_cookie(name,value,days) {

  if (days) {

    var date = new Date();

    date.setTime(date.getTime()+(days*24*60*60*1000));

    var expires = "; expires="+date.toGMTString();

  }

  else expires = "";

  document.cookie = name+"="+value+expires+"; path=/";

}



function read_cookie(name) {

  var nameEQ = name + "=";

  var ca = document.cookie.split(';');

  for(var i=0;i < ca.length;i++) {

    var c = ca[i];

    while (c.charAt(0)==' ') c = c.substring(1,c.length);

    if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);

  }

  return null;

}



window.onload = function(e) {

  var cookie = read_cookie("style");

  var title = cookie ? cookie : get_preferred_sheet();

  set_active_sheet(title);

}



window.onunload = function(e) {

  var title = get_active_sheet();

  create_cookie("style", title, 365);

}



var cookie = read_cookie("style");

var title = cookie ? cookie : get_preferred_sheet();

set_active_sheet(title);

Als nächstes muss man noch Links definieren, die den Swicht des Stylesheets auslösen:

<a href="./" onClick="setActiveStyleSheet('big'); return false;">Schriftgröße rauf</a>

<a href="./" onClick="setActiveStyleSheet('small'); return false;">Schriftgröße runter</a>