框架有2个行为：框架作为文档元素（如div或其他DOM）元素）和框架作为窗口元素（如全局窗口对象）。因此，如果你想从DOM树中删除iframe，你必须使用与DOM元素一样的iframe

Frame has 2 behaviors: frame as document element (like div or another DOM element) and frame as window element (like global window object). So if you want to remove iframe from DOM tree you have to work with iframe like with DOM element

function remove(){
 var frame = document.getElementById("upload_iframe");
 frame.parentNode.removeChild(frame);
}