A bug in how IE handles the onload event of GIF animated images

In IE, if you create an image object and then add an onload event to load a GIF animated image, the onload execution method will be executed repeatedly, but this problem does not occur in browsers other than IE.

 

 <Script type = "text/javascript">
Var img = new Image ();
Img. src = "test.gif ";
Img. onload = function (){
Alert ("This will be repeated! ");
}
</Script>

 

After research, it is found that this is because there are multiple frames in the GIF animation, each frame will trigger an onload event, so the onload method will be executed all the time, knowing the cause is easy to solve.

 <Script type = "text/javascript">
Var img = new Image ();
Img. src = "test.gif ";
Img. onload = function (){
Alert ("Loading completed, only once ");
Img. onload = null; // This is the key point.
}
</Script>

 

After loading, assign the onload event to null, so that no onload event can be triggered when the img is animated to the next frame.