is演算子

is演算子は A is B　の書式で使用し、Bはクラス名、Aは変数
Aのクラスが、BもしくはBを継承したクラスである場合はtrue、違う場合はfalse

var clip:MovieClip=new MovieClip();
var sprite:Sprite = new Sprite();

if(clip is MovieClip){
trace("clip is MovieClip:true");
}else{
trace("clip is MovieClip：false");
}

if(clip is Sprite){
trace("clip is Sprite:true");
}else{
trace("clip is Sprite：false");
}

if(clip is DisplayObjectContainer){
trace("clip is DisplayObjectContainer:true");
}else{
trace("clip is DisplayObjectContainer：false");
}

if(sprite is MovieClip){
trace("sprite is MovieClip:true");
}else{
trace("sprite is MovieClip：false");
}

if(sprite is Sprite){
trace("sprite is Sprite:true");
}else{
trace("sprite is Sprite：false");
}

if(sprite is DisplayObjectContainer){
trace("sprite is DisplayObjectContainer:true");
}else{
trace("sprite is DisplayObjectContainer：false");
}

結果：
clip is MovieClip:true
clip is Sprite:true
clip is DisplayObjectContainer:true
sprite is MovieClip：false
sprite is Sprite:true
sprite is DisplayObjectContainer:true