Question

When creating a new Image element in javascript, Google Chrome’s memory tool (Developer tools > Timeline > Memory) considers it as a new DOM element, naturally.

In my case, I’m ending up with 1500+ DOM elements, and I wish to get rid of them. I have tried to save all objects in an array and delete all of them in a loop when I’m ready creating all objects, resulting in the following error:

Uncaught TypeError: Cannot call method 'removeChild' of null

That indicates the Image objects doesn’t appear in the actual DOM.

var images = [];
var i, image;

for( i = 0; i < urls.length; i++ ) {
    image = new Image();
    image.src = urls[i];
}

// other stuff happens

for( i = 0; i < images.length; i++ ) {
    // apparently this doesn't work because I'm not adding the image to my DOM
    // images[i].parentNode.removeChild( images[i] );

    // delete images
}

Is there a way to remove/delete/unset/dispose the Image objects?

Answer 1

Setting images = null would remove your reference in code to the object. However, to implement its load event, Chrome has to have its own internal reference to the object.

That is, you could have code like this:

for( i = 0; i < urls.length; i++ ) { 
    image = new Image(); 
    image.src = urls[i]; 
    image.onload = function(){alert('Test');};
    image = null;
} 

This way you would still get a lot of “Test” alerts, even though you do not have a reference to these objects.

Hence, my guess is that it is a bug in Chrome, not in your code.

Update: looking through the Chromium source sort of proves that (I mean the comment on lines 67-71 of this file, especially the FIXME note http://code.google.com/searchframe#OAMlx_jo-ck/src/third_party/WebKit/Source/WebCore/bindings/v8/custom/V8HTMLImageElementConstructor.cpp ):

// Make sure the document is added to the DOM Node map. Otherwise, the HTMLImageElement instance
// may end up being the only node in the map and get garbage-ccollected prematurely.
// FIXME: The correct way to do this would be to make HTMLImageElement derive from
// ActiveDOMObject and use its interface to keep its wrapper alive. Then we would
// remove this code and the special case in isObservableThroughDOM.