Check whether browser exists or not?

function BrowserExists() 
{                
   //Check if browser is IE or not 
   if (navigator.userAgent.search("MSIE") >= 0) {
      alert("Browser is InternetExplorer");
   }
   //Check if browser is Chrome or not 
   else if (navigator.userAgent.search("Chrome") >= 0) {
      alert("Browser is Chrome");
   }
   //Check if browser is Firefox or not 
   else if (navigator.userAgent.search("Firefox") >= 0) {
       alert("Browser is FireFox");
   }
   //Check if browser is Safari or not 
   else if (navigator.userAgent.search("Safari") >= 0 && navigator.userAgent.search("Chrome") < 0) {
       alert("Browser is Safari");
   }
   //Check if browser is Opera or not 
   else if (navigator.userAgent.search("Opera") >= 0) {
       alert("Browser is Opera");
   }
}