In questo articolo vedremo come modificare lo stile css di una pagina web con uno script javascript. Nella pagina html, avremo l'elenco degli stili:
...
<link rel="stylesheet" type="text/css" href="stile1.css" title="stile1" />
<link rel="alternate stylesheet" type="text/css" href="stile2.css" title="stile2" />
...
e oltre al resto della pagina, la chiamata al file javascript:
<script type="text/javascript" src="switcher.js"></script>
cosi impostato:
/* Style Switcher by Paul Sowden, see A List Apart: http://www.alistapart.com/articles/alternate/ */
function setActiveStyleSheet(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 getActiveStyleSheet() {
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 getPreferredStyleSheet() {
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 createCookie(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 readCookie(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 = readCookie("style");
var title = cookie ? cookie : getPreferredStyleSheet();
setActiveStyleSheet(title);
}
window.onunload = function(e) {
var title = getActiveStyleSheet();
createCookie("style", title, 365);
}
var cookie = readCookie("style");
var title = cookie ? cookie : getPreferredStyleSheet();
setActiveStyleSheet(title);
document.writeln("<div id=\"textsize\">Passa a stile1: <a href=\"#\" onclick=\"setActiveStyleSheet('stile1'); return false;\" id=\"stile1\">Stile1</a><a href=\"#\" onclick=\"setActiveStyleSheet('stile2'); return false;\" id=\"stile2\">Passa a stile2</a></div>");
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