How to judge whether 1 JS in iframe(http://www.programering.com/a/MDOwMzMwATg.html)

judgeINIframe

//One way
if (self.frameElement && self.frameElement.tagName == "IFRAME") {
         alert('In iframe');
}
//Methods two
if (window.frames.length != parent.frames.length) {
         alert('In iframe');
}
//Fang Shisan
if (self != top) {  
     alert('In iframe');
}