Как сделать чтобы скрипт сам не срабатывал при загрузке страницы, а запускался только по кнопкам вкл и выкл

var snowsrc = "http://all-blogspot.com/blog/img/snow.png"; 
var no = 40; 
var log = 1; 
var hidesnowtime = 0; 
var snowdistance = "windowheight"; 
 
var ie4up = (document.all) ? 1 : 0; 
var ns6up = (document.getElementById && !document.all) ? 1 : 0; 
 
function iecompattest() { 
  return (document.compatMode && document.compatMode != "BackCompat") ? document.documentElement : document.body 
} 
 
var dx, xp, yp; 
var am, stx, sty; 
var i, doc_width = 800, 
  doc_height = 600; 
 
if (ns6up) { 
  doc_width = self.innerWidth; 
  doc_height = self.innerHeight; 
} else if (ie4up) { 
  doc_width = iecompattest().clientWidth; 
  doc_height = iecompattest().clientHeight; 
} 
 
dx = new Array(); 
xp = new Array(); 
yp = new Array(); 
am = new Array(); 
stx = new Array(); 
sty = new Array(); 
snowsrc = (snowsrc.indexOf("all-blogspot.com") != 1) ? "http://all-blogspot.com/blog/img/snow.png" : snowsrc; 
for (i = 0; i < no; ++i) { 
  dx[i] = 0; 
  xp[i] = Math.random() * (doc_width - 50); 
  yp[i] = Math.random() * doc_height; 
  am[i] = Math.random() * 20; 
  stx[i] = 0.02 + Math.random() / 10; 
  sty[i] = 0.7 + Math.random(); 
  if (ie4up || ns6up) { 
    if (i == 0) { 
      document.write("<div id=\"dot" + i + "\" style=\"visibility:hidden;POSITION: fixed; Z-INDEX: " + i + "; VISIBILITY: visible; TOP: 15px; LEFT: 15px;\"><img src='" + snowsrc + "' border=\"0\"><\/div>"); 
    } else { 
      document.write("<div id=\"dot" + i + "\" style=\"visibility:hidden;POSITION: fixed; Z-INDEX: " + i + "; VISIBILITY: visible; TOP: 15px; LEFT: 15px;\"><img src='" + snowsrc + "' border=\"0\"><\/div>"); 
    } 
  } 
} 
hidesnow(); 
 
function snowIE_NS6() { 
  doc_width = ns6up ? window.innerWidth - 10 : iecompattest().clientWidth - 10; 
  doc_height = (window.innerHeight && snowdistance == "windowheight") ? window.innerHeight : (ie4up && snowdistance == "windowheight") ? iecompattest().clientHeight : (ie4up && !window.opera && snowdistance == "pageheight") ? iecompattest().scrollHeight : iecompattest().offsetHeight; 
  for (i = 0; i < no; ++i) { 
    yp[i] += sty[i]; 
    if (yp[i] > doc_height - 50) { 
      xp[i] = Math.random() * (doc_width - am[i] - 30); 
      yp[i] = 0; 
      stx[i] = 0.02 + Math.random() / 10; 
      sty[i] = 0.7 + Math.random(); 
    } 
    dx[i] += stx[i]; 
    document.getElementById("dot" + i).style.top = yp[i] + "px"; 
    document.getElementById("dot" + i).style.left = xp[i] + am[i] * Math.sin(dx[i]) + "px"; 
  } 
  snowtimer = setTimeout("snowIE_NS6()", 10); 
} 
 
function hidesnow() { 
  if (window.snowtimer) clearTimeout(snowtimer) 
  for (i = 0; i < no; i++) document.getElementById("dot" + i).style.visibility = "hidden"; 
} 
 
if (ie4up || ns6up) { 
  snowIE_NS6(); 
  if (hidesnowtime > 0) 
    setTimeout("hidesnow()", hidesnowtime * 1000); 
} 
 
function stopsnow() { 
  if (log == 0) { 
    for (i = 0; i < no; i++) document.getElementById("dot" + i).style.visibility = "hidden"; 
    //no = 0; 
    log = 1; 
    document.getElementById('snow-start').innerHTML = 'Вкл. снег'; 
  } else { 
    log = 0; 
    //no = 20; 
    for (i = 0; i < no; i++) document.getElementById("dot" + i).style.visibility = "visible"; 
    document.getElementById('snow-start').innerHTML = 'Выкл. снег'; 
 
  } 
 
}

#snow-start { 
  background: rgba(27, 25, 25, 0.4); 
  color: #fff; 
  display: inline-block; 
  width: 100px; 
  text-align: center; 
  cursor: pointer; 
  line-height: 25px; 
  position: fixed; 
  right: 0px; 
  top: 0px; 
  border-radius: 0px 0px 0px 9px; 
} 
 
#copy { 
  color: rgba(20, 16, 16, 0); 
  font-size: 7px; 
  position: fixed; 
  text-decoration: none; 
  top: 24px; 
  right: 2px; 
}

<div onclick="stopsnow()" id="snow-start">Вкл. снег</div> 
<a id="copy" href="http://all-blogspot.com/"></a>