js关闭窗口后弹出信息

代码

function addOnBeforeUnload(e) {

var ev = e || event;

    ev && (ev.returnValue ='你确定要离开？');

}

if (window.attachEvent) {

window.attachEvent('onbeforeunload', addOnBeforeUnload);

}else {

window.addEventListener('beforeunload', addOnBeforeUnload, false);

}