我正在尝试让 GM_xmlhttpRequest 调用同步运行，但我无法让它像我期望的那样工作:

I'm trying to get a GM_xmlhttpRequest call to behave synchronously, but I can't get it to work like I expect:

function myFunction (arg) {
    var a;

    GM_xmlhttpRequest ( {
        method:         "GET",
        url:            "http://example.com/sample/url",
        synchronous:    true,

        onload: function (details) {
            a = details.responseText;
        }
    } );

    return a;
}
b = myFunction ();
alert (b);

b 在这里我再也没有得到任何回报；它是未定义的.我在这里缺少一些步骤吗?我正在使用 v0.9.13 的 Greasemonkey 和 v9.0.1 的 Firefox.

I never get anything back for b here; it's undefined. Is there some step that I'm missing here? I'm using v0.9.13 of Greasemonkey, and v9.0.1 of Firefox.

推荐答案

刚刚在 Google 上偶然发现了这个话题.

Just stumbled upon this topic in Google.

同步 GM_xmlhttpRequest 返回结果，而不是在 onload-callback 中执行.

Synchronous GM_xmlhttpRequest RETURN the result instead of executing it in the onload-callback.

所以这是对的:

var details = GM_xmlhttpRequest({
  method:"GET",
  url:"http://site.com/sample/url",
  synchronous: true
});
a = details.responseText;

您在开始时创建了 var "a"，从不填充它并返回它.因此，它是未定义的.

You create the var "a" in the beginning, never fill it and return it. Therefore, it is undefined.