如何从iframe中获取所选文本(处理IE)

function getIframeSelectionText(iframe) {
    var win, doc = iframe.contentDocument;
    if (doc) {
        win = doc.defaultView;
    } else {
        win = iframe.contentWindow;
        doc = win.document;
    }

    if (win.getSelection) {
        return win.getSelection().toString();
    } else if (doc.selection && doc.selection.createRange) {
        return doc.selection.createRange().text;
    }
}

var iframe = document.getElementById("your_iframe");
alert( getIframeSelectionText(iframe) );