View source for How to determine browser capabilities/en

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Web browsers sometimes differ in the way they render a page. For this reason you may wish to find out which particular browser a visitor is using in order to use some browser-specific CSS.

The following JavaScript defines a simple browser detection object that determines the browser's name and version by decoding the ''navigator.userAgent'' string.

<syntaxhighlight lang="javascript">
function browserDetect()
{
  var browserNames=new Array("Opera", "MSIE","Netscape","Firefox");
  this.name="NK";
  this.mainVersion="NK";
  this.minorVersion="NK";
  
  for (var i=0; i< browserNames.length; i++)
  {
   var pattern='('+browserNames[i]+')'+'.([0-9]+)\.([0-9]+)';    
   var myRegExp=new RegExp(pattern);
   if (myRegExp.test(navigator.userAgent))
    {
      var results=myRegExp.exec(navigator.userAgent);
      this.name=results[1];
      this.mainVersion=results[2];
      this.minorVersion=results[3];
      break;
    }
  }
}
</syntaxhighlight>

To use this in a script, you create an instance of this object:

<syntaxhighlight lang="javascript">
var browser = new browserDetect();
</syntaxhighlight>

The property ''browser.name'' will then give you the name of the browser (MSIE, Opera, Netscape or Firefox), ''browser.mainVersion'' will show the main version number and ''browser.minorVersion'' contains the minor version number.

This is not foolproof. It is much better to avoid writing browser-specific code.

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