帮助我理解以下与 AsyncFileUpload 控件相关的 javascript

发布于 2024-09-02 17:53:27 字数 882 浏览 4 评论 0原文

在我当前的项目中，我使用了 AJAX 控件工具包中的 AsyncFileUpload 控件。在异步文件上传部分工作后，我需要过滤文件类型，以便用户只能上传图像文件。我在网上找到了以下代码，它运行良好：

function uploadStarted(sender, args) {  
        var filename = args.get_fileName();  
        var filext = filename.substring(filename.lastIndexOf(".") + 1);  
        if (filext == "jpg" || filext == "jpeg" || filext == "gif" || filext == "bmp")      {
            return true;
        }
        else 
        {  
            // force uploading cancel  
            args.set_cancel(true);  
            // set reason of cancel  
            args.set_errorMessage("Invalid File Format Selected");  
            return false;  
        }  
    }

问题是：我不明白这个 javascript。 args 参数的类型是什么？ “get_fileName()”、“set_cancel()”等方法在哪里定义？我访问了 AsyncFileUpload 控件的主页，但找不到任何有关“args”的文档。

有人可以帮我解释一下这个Javascript吗？谢谢

原文

in my current project I used a AsyncFileUpload control from AJAX Control Toolkits. After I got the async file upload part working, I needed to filter the file type so users can only upload image files. I found the following code off web and it worked well:

function uploadStarted(sender, args) {  
        var filename = args.get_fileName();  
        var filext = filename.substring(filename.lastIndexOf(".") + 1);  
        if (filext == "jpg" || filext == "jpeg" || filext == "gif" || filext == "bmp")      {
            return true;
        }
        else 
        {  
            // force uploading cancel  
            args.set_cancel(true);  
            // set reason of cancel  
            args.set_errorMessage("Invalid File Format Selected");  
            return false;  
        }  
    }

The problem is : I don't understand this javascript. What is the type of args parameter? Where are the methods such as "get_fileName()", "set_cancel()" defined? I went to the homepage of the AsyncFileUpload control but couldn't find any documentation regarding the "args".

Can someone help me out explaining this Javascript? Thanks

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