这里有两件事:

首先，由于没有其他查询字符串，因此您的网址添加项应为"?callback=?"，或使用完整的 数据类型为jsonp的调用，以便根据需要添加查询字符串，如下所示:

$.ajax({
  url: resturl,
  dataType: 'jsonp',
  success: function(data){
    console.log( data );
  }
});

第二，您要使用的域必须支持 JSONP .>

var resturl = "http://example.com";
cj.getJSON(
    resturl + "&callback=?",        
    function(data)
    {
       console.log( data );
    }
);

My callback function is never called. Any ideas?

Two things here:

First your URL additon should be "?callback=?" since there's no other querystring, or use the full $.ajax() call with a jsonp data type so it adds the querystring as needed, like this:

$.ajax({
  url: resturl,
  dataType: 'jsonp',
  success: function(data){
    console.log( data );
  }
});

Second, the domain you're going to has to support JSONP.