JavaScript/MooTools: IE 6?

What's the easiest way to tell if the browse开发者_StackOverflowr is an IE 6 version in JavaScript? We're using MooTools here and Browser.Engine.trident will be true if it's IE, but what about the version number?

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if (Browser.Engine.trident4) alert('is IE6');

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Just to keep this up to date. Most current version of Mootools you need:

if (Browser.ie6) alert('is IE6');