Javascript:onbeforeunload 不工作

Question

下面的代码有什么问题？

<script language="javascript">
    function abreJanela() {
        var janela = window.open("http://www.google.com", "janela", "width=700, height=600");

        janela.onbeforeunload = function() {
            alert("Windows was closed");

        }
    }
</script>

Answer 1

onbeforeunload 的目的是返回一个字符串，(通常)用于提示用户。其他操作，如 alert，可能会(通常会)被忽略。请看the Mozilla Developer Network documentation :

Since 25 May 2011, the HTML5 specification states that calls to window.alert(), window.confirm(), and window.prompt() methods may be ignored during this event. See the HTML5 specification for more details.