Check what browser

function myFunction() { 
     if((navigator.userAgent.indexOf("Opera") || navigator.userAgent.indexOf('OPR')) != -1 ) 
    {
        alert('Opera');
    }
    else if(navigator.userAgent.indexOf("Chrome") != -1 )
    {
        alert('Chrome');
    }
    else if(navigator.userAgent.indexOf("Safari") != -1)
    {
        alert('Safari');
    }
    else if(navigator.userAgent.indexOf("Firefox") != -1 ) 
    {
         alert('Firefox');
    }
    else if((navigator.userAgent.indexOf("MSIE") != -1 ) || (!!document.documentMode == true )) //IF IE > 10
    {
      alert('IE'); 
    }  
    else 
    {
       alert('unknown');
    }
}