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if (!(window.ActiveXObject) && "ActiveXObject" in window) {
  //do something
}

// OR

if(window.navigator.userAgent.indexOf('MSIE')!==-1
|| window.navigator.appVersion.indexOf('Trident/') > 0){
   /* Microsoft Internet Explorer detected in. */
}

// OR

function GetIEVersion() {
  var sAgent = window.navigator.userAgent;
  var Idx = sAgent.indexOf("MSIE");

  // If IE, return version number.
  if (Idx > 0) 
    return parseInt(sAgent.substring(Idx+ 5, sAgent.indexOf(".", Idx)));

  // If IE 11 then look for Updated user agent string.
  else if (!!navigator.userAgent.match(/Trident\/7\./)) 
    return 11;

  else
    return 0; //It is not IE
}

//checker
if (GetIEVersion() > 0) 
   alert("This is IE " + GetIEVersion());
else 
   alert("This is not IE.");