限制上传文件大小和格式的jQuery插件实例

(function ($) {
    $.fn.checkFileTypeAndSize = function (options) {
        //默认设置
        var defaults = {
            allowedExtensions: [],
            maxSize: 1024, //单位是KB，默认最大文件尺寸1MB=1024KB
            suess: function () { },
            extensionerror: function () { },
            sizeerror: function () { }
        };
        //合并设置
        options = $.extend(defaults, options);
        //遍历元素
        return this.each(function () {
            $(this).on('change', function () {
                //获取文件路径
                var filePath = $(this).val();
                //小写字母的文件路径
                var fileLowerPath = filePath.toLowerCase();
                //获取文件的后缀名
                var extension = fileLowerPath.substring(fileLowerPath.lastIndexOf('.') + 1);
                //判断后缀名是否包含在预先设置的、所允许的后缀名数组中
                if ($.inArray(extension, options.allowedExtensions) == -1) {
                    options.extensionerror();
                    $(this).focus();
                } else {
                    try {
                        var size = 0;
                        if ($.browser.msie) {//ie旧版浏览器
                            var fileMgr = new ActiveXObject("Scripting.FileSystemObject");
                            var fileObj = fileMgr.getFile(filePath);
                            size = fileObj.size; //byte
                            size = size / 1024;//kb
                            //size = size / 1024;//mb
                        } else {//其它浏览器
                            size = $(this)[0].files[0].size;//byte
                            size = size / 1024;//kb
                            //size = size / 1024;//mb
                        }
                        if (size > options.maxSize) {
                            options.sizeerror();
                        } else {
                            options.suess();
                        }
                    } catch (e) {
                        alert("错误" + e);
                    }
                }
            });
        });
    };
})(jQuery);

<input type="file" name="f" id="f"/>
@section scripts
{
    <script src="~/Scripts/checkFileTypeAndSize.js"></script>
    <script type="text/javascript">
        $(function() {
            $('#f').checkFileTypeAndSize({
                allowedExtensions: ['jpg'],
                maxSize: 10,
                suess: function() {
                    alert('ok');
                },
                extensionerror: function() {
                    alert('允许的格式为jpg');
                    return;
                },
                sizeerror: function() {
                    alert('最大尺寸10kb');
                    return;
                }
            });
        });
    </script>
}