如何将id作为FileUpload的参数传递给javascript函数以检查文件的扩展名和大小

我正在开发asp.net web应用程序，其中有6个文件上载控件 对于一个文件上传，我创建了一个javascript方法来检查文件扩展名和文件大小。 但如何动态地传递FileUpload的id，以便只有一种方法可以验证所有FileUpload 我的JavaScript代码是

  var validFilesTypes = ["bmp", "gif", "png", "jpg", "jpeg", "doc", "docx",         "xls", "xlsx", "htm", "html", "rar", "zip", "txt", "pdf"];
    function CheckExtension() {
        /*global document: false */
        var file = document.getElementById("<%=txtTenderDoc.ClientID%>");
        var path = file.value;
        var ext = path.substring(path.lastIndexOf(".") + 1, path.length).toLowerCase();
        var isValidFile = false;
        for (var i = 0; i < validFilesTypes.length; i++) {
            if (ext == validFilesTypes[i]) {
                isValidFile = true;
                break;
            }
        }
        if (!isValidFile) {
            alert("Invalid File. Unknown Extension Of Tender Doc" + "Valid extensions are:\n\n" + validFilesTypes.join(", "));
        }
        return isValidFile;
    }

    function validateFileSize() {
        /*global document: false */
        var file = document.getElementById("<%=txtTenderDoc.ClientID%>");
        var fileSize = file.files[0].size;
        var isValidFile = false;
        if (fileSize !== 0 && fileSize <= 25214400) {
            isValidFile = true;
        }
        if (!isValidFile) {
            alert("File Size Should be Greater than 0 and less than 25 mb");
        }
        return isValidFile;
    }

var validFileTypes=[“bmp”、“gif”、“png”、“jpg”、“jpeg”、“doc”、“docx”、“xls”、“xlsx”、“htm”、“html”、“rar”、“zip”、“txt”、“pdf”]；
函数CheckExtension（）{
/*全局文档：false*/
var file=document.getElementById（“”）；
var path=file.value；
var ext=path.substring（path.lastIndexOf（“.”+1，path.length）.toLowerCase（）；
var isValidFile=false；
对于（变量i=0；i函数检查扩展名（Id）{
/*全局文档：false*/
var file=document.getElementById（Id）；
var path=file.value；
var ext=path.substring（path.lastIndexOf（“.”+1，path.length）.toLowerCase（）；
var isValidFile=false；
对于（变量i=0；i如果（fileSize！==0&&fileSize在网上搜索后，我终于解决了这个问题并发布了它，如果有人有类似的问题，这应该会有所帮助

 // set which files are allowed in FileUpload Control
    var validFilesTypes = ["bmp", "gif", "png", "jpg", "jpeg", "doc", "docx", "xls", "xlsx", "htm", "html", "rar", "zip", "txt", "pdf"];
    function CheckExtension(file) {
        /*global document: false */
        var path = file.value;
        var ext = path.substring(path.lastIndexOf(".") + 1, path.length).toLowerCase();
        var isValidFile = false;
        for (var i = 0; i < validFilesTypes.length; i++) {
            if (ext == validFilesTypes[i]) {
                isValidFile = true;
                break;
            }
        }
        if (!isValidFile) {
            alert("Invalid File. Unknown Extension Of Tender Doc" + "Valid extensions are:\n\n" + validFilesTypes.join(", "));
        }
        return isValidFile;
    }

    function validateFileSize(file) {
        /*global document: false */
        //getting size of the file
        var fileSize = file.files[0].size;
        var isValidFile = false;
        if (fileSize !== 0 && fileSize <= 25214400) {
            isValidFile = true;
        }
        if (!isValidFile) {
            alert("File Size Should be Greater than 0 and less than 25 mb");
        }
        return isValidFile;
    }

//设置FileUpload控件中允许的文件
var validFileTypes=[“bmp”、“gif”、“png”、“jpg”、“jpeg”、“doc”、“docx”、“xls”、“xlsx”、“htm”、“html”、“rar”、“zip”、“txt”、“pdf”]；
函数检查扩展名（文件）{
/*全局文档：false*/
var path=file.value；
var ext=path.substring（path.lastIndexOf（“.”+1，path.length）.toLowerCase（）；
var isValidFile=false；
对于（变量i=0；iif（fileSize！==0&&fileSize我尝试过这个方法，在firebug中我得到了错误Uncaught Typeerror:无法读取此行附近null的属性'value'，var path=file.value；您需要检查传入的Id值，看看它是否与页面中绘制的输入匹配。可能也应该检查文件是否为null。
function CheckExtension(Id) {
    /*global document: false */
    var file = document.getElementById(Id);
    var path = file.value;
    var ext = path.substring(path.lastIndexOf(".") + 1, path.length).toLowerCase();
    var isValidFile = false;
    for (var i = 0; i < validFilesTypes.length; i++) {
        if (ext == validFilesTypes[i]) {
            isValidFile = true;
            break;
        }
    }
    if (!isValidFile) {
        alert("Invalid File. Unknown Extension Of Tender Doc" + "Valid extensions are:\n\n" + validFilesTypes.join(", "));
    }
    return isValidFile;
}   


function validateFileSize(Id) {
    /*global document: false */
    var file = document.getElementById(Id);
    var fileSize = file.files[0].size;
    var isValidFile = false;
    if (fileSize !== 0 && fileSize <= 25214400) {
        isValidFile = true;
    }
    if (!isValidFile) {
        alert("File Size Should be Greater than 0 and less than 25 mb");
    }
    return isValidFile;
}

<asp:FileUpload ID="txtTenderDoc" onchange="var result=      CheckExtension('textTenderDoc');validateFileSize('textTenderDoc'); return result"  runat="server"></asp:FileUpload>

 // set which files are allowed in FileUpload Control
    var validFilesTypes = ["bmp", "gif", "png", "jpg", "jpeg", "doc", "docx", "xls", "xlsx", "htm", "html", "rar", "zip", "txt", "pdf"];
    function CheckExtension(file) {
        /*global document: false */
        var path = file.value;
        var ext = path.substring(path.lastIndexOf(".") + 1, path.length).toLowerCase();
        var isValidFile = false;
        for (var i = 0; i < validFilesTypes.length; i++) {
            if (ext == validFilesTypes[i]) {
                isValidFile = true;
                break;
            }
        }
        if (!isValidFile) {
            alert("Invalid File. Unknown Extension Of Tender Doc" + "Valid extensions are:\n\n" + validFilesTypes.join(", "));
        }
        return isValidFile;
    }

    function validateFileSize(file) {
        /*global document: false */
        //getting size of the file
        var fileSize = file.files[0].size;
        var isValidFile = false;
        if (fileSize !== 0 && fileSize <= 25214400) {
            isValidFile = true;
        }
        if (!isValidFile) {
            alert("File Size Should be Greater than 0 and less than 25 mb");
        }
        return isValidFile;
    }

<asp:FileUpload ID="fuTenderDoc" onchange="var result=CheckExtension(this);validateFileSize(this); return result"
                        runat="server"></asp:FileUpload>

<asp:FileUpload ID="fuBidDoc" onchange="var result=CheckExtension(this);validateFileSize(this); return result"
                        runat="server"></asp:FileUpload>

 <asp:FileUpload ID="fuTechnicalDoc" onchange="var result=CheckExtension(this);validateFileSize(this); return result"
                        runat="server"></asp:FileUpload>