var sec=0;
var min=0;
var sw_enb=true;

onload=function init(){
  document.getElementById("stopwatch").innerHTML="00:00";
  document.getElementById("stopwatch_button").innerHTML='<input type="button" onclick="sw_ss()" value="Start" id="swsw" class="swatch_but">';
}
function sw_ss(){
if(document.getElementById("swsw").value=="Start"){
  setTimeout("incsec()",1000);
  sw_enb=true;
  sec=0;
  min=0;
  document.getElementById("stopwatch").innerHTML="00:00";
  document.getElementById("swsw").value="Stop";
}
else{
  sw_enb=false;
  document.getElementById("swsw").value="Start";
}
}
function incsec(){
if(sw_enb){
  setTimeout("incsec()",1000);
  sec++;
  if(sec>=60){
    sec-=60;
    min++;
  }
  var tstr="";
  if(min<10){
    tstr="0"+min+":";
  }
  else{
    tstr=min+":";
  }
  if(sec<10){
    tstr+="0"+sec;
  }
  else{
    tstr+=sec;
  }
  document.getElementById("stopwatch").innerHTML=tstr;
  if(sec==59 && min==99){
    sw_enb=false;
  }
}
}