window beforeunload 事件

回调方法里面只能返回 字符串

window.onbeforeunload = funcRef

• funcRef is a reference to a function or a function expression
• The function should assign a string value to the returnValue property of the Event object and return the same string

window.onbeforeunload = function(e) {

    return 'Dialog text here.';

};

jQuery(window).unbind("beforeunload").bind("beforeunload", function() {
return ' ';
});