WordPress媒体上传器javascript

Question

我有以下代码，我以前曾在自定义插件页面中成功打开wordpress媒体上传器。

var custom_uploader;

jQuery('#uploadButton').click(function(e) { 
    e.preventDefault(); 
    //Extend the wp.media object
    custom_uploader = wp.media.frames.file_frame = wp.media({
        title: 'Choose Image',
        button: {
            text: 'Choose Image'
        },
        multiple: false
    }); 
    //When a file is selected, grab the URL and set it as the text field's value
    custom_uploader.on('select', function() {
        var attachment = custom_uploader.state().get('selection').first().toJSON();
    alert(attachment.url);
    }); 
    //Open the uploader dialog
    custom_uploader.open(); 

}); 

现在失败并显示消息＆＃34;上传时出错。请稍后再试。＆＃34;。我在这里做错了吗？