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Browser Sniffing

Status:Draft
Version:1.0
Authors:Peter Higgins, Ben Lowery

You should try to use capability detection (http://dev.opera.com/articles/view/using-capability-detection/) when possible. When that is not an option, Dojo provides a number of is variables for browser detection, defined at runtime based on the users current browser.

  • dojo.isIE
  • dojo.isMozilla
  • dojo.isFF
  • dojo.isOpera
  • dojo.isSafari
  • dojo.isKhtml
  • dojo.isAIR - true if running within the Adobe AIR enviroment
  • dojo.isQuirks - is the browser in Quirks-Mode
  • dojo.isBrowser (not typically needed when only targeting browsers)

For Dojo 1.3, the following were added:

  • dojo.isWebKit
  • dojo.isChrome

Each variable is only defined if the specified browser is being used. For example, if you’re using Internet Explorer, only dojo.isIE is defined; all the other variables are undefined. The variable holds the browser version number as a Number, so you can easily perform version checks. Additionally, since undefined always evaluates as false in if statements, you can use code like this to check for a certain browser version:

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if(dojo.isIE <= 6){ // only IE6 and below
  ...
}
if(dojo.isFF < 3){ // only Firefox 2.x and lower
  ...
}
if(dojo.isIE == 7){ // only IE7
  ...
}

Examples

Here's a live sample to show how it works:

<script type="text/javascript">
function makeFancyAnswer(who){
  if(dojo["is" + who]){
    return "Yes, it's version " + dojo["is" + who];
  }else{
    return "No";
  }
}
function makeAtLeastAnswer(who, version) {
  var answer = (dojo["is" + who] >= version) ? "Yes" : "No";
  dojo.byId("isAtLeast" + who + version).innerHTML = answer;
}
dojo.addOnLoad(function(){
  dojo.forEach(["IE", "Mozilla", "FF", "Opera", "WebKit", "Chrome"],
               function(n) {
                 dojo.byId("answerIs" + n).innerHTML = makeFancyAnswer(n);
               });
  makeAtLeastAnswer("IE", 7);
  makeAtLeastAnswer("FF", 3);
  makeAtLeastAnswer("Opera", 9);
});
</script>
<dl>
  <dt>Is this Internet Explorer?</dt>
  <dd id="answerIsIE"></dd>
  <dt>Is this Firefox?</dt>
  <dd id="answerIsFF"></dd>
  <dt>Is this Mozilla?</dt>
  <dd id="answerIsMozilla"></dd>
  <dt>Is this Opera?</dt>
  <dd id="answerIsOpera"></dd>
  <dt>Is this WebKit? (Dojo 1.3)</dt>
  <dd id="answerIsWebKit"></dd>
  <dt>Is this Chrome? (Dojo 1.3)</dt>
  <dd id="answerIsChrome"></dd>
</dl>
<dl>
  <dt>Is this at least IE 7?</dt>
  <dd id="isAtLeastIE7"></dd>
  <dt>Is this at least Firefox 3?</dt>
  <dd id="isAtLeastFF3"></dd>
  <dt>Is this at least Opera 9?</dt>
  <dd id="isAtLeastOpera9"></dd>
</dl>