Js离开提示

<script type="text/javascript">
    var g_blnCheckUnload = true;
    var isEdit = true;
    var currentEditorId = 'Editor_Edit_EditorBody';
    var currentUseEditor = 3;

    function insertDescImg() {
        var imgSrc = prompt('请输入图片网址', 'http://');
        if (!imgSrc) {
            return false;
        }
        //var strImg ="<div style=\"float:right\" class=\"descImg\"><img src=\""+imgSrc+ "\"></div>";
        var strImg = "<img src=\"" + imgSrc + "\" class=\"desc_img\"/>";
        document.getElementById("Editor_Edit_Advanced_txbExcerpt").value = strImg + document.getElementById("Editor_Edit_Advanced_txbExcerpt").value;
        document.getElementById("Editor_Edit_Advanced_txbExcerpt").focus();
        return false;
    }

    function BypassCheck() { g_blnCheckUnload = false; }