jquery怎么限制文本框只能输入数字？

$("input[name='fangwenyudinhuishu']").keyup(function(){    
  var tmptxt=$(this).val();    
  $(this).val(tmptxt.replace(/D|^0/g,''));    
}).bind("paste",function(){    
  var tmptxt=$(this).val();    
  $(this).val(tmptxt.replace(/D|^0/g,''));    
}).css("ime-mode", "disabled");   

$(function(){ 
 //文本框只能输入数字，并屏蔽输入法和粘贴 
 $.fn.numeral = function() {    
            $(this).css("ime-mode", "disabled");    
            this.bind("keypress",function(e) {    
            var code = (e.keyCode ? e.keyCode : e.which);  //兼容火狐 IE     
                if(!$.browser.msie&&(e.keyCode==0x8))  //火狐下不能使用退格键    
                {    
                     return ;    
                    }    
                    return code >= 48 && code<= 57;    
            });    
            this.bind("blur", function() {    
                if (this.value.lastIndexOf(".") == (this.value.length - 1)) {    
                    this.value = this.value.substr(0, this.value.length - 1);    
                } else if (isNaN(this.value)) {    
                    this.value = "";    
                }    
            });    
            this.bind("paste", function() {    
                var s = clipboardData.getData('text');    
                if (!/D/.test(s));    
                value = s.replace(/^0*/, '');    
                return false;    
            });    
            this.bind("dragenter", function() {    
                return false;    
            });    
            this.bind("keyup", function() {    
            if (/(^0+)/.test(this.value)) {    
                this.value = this.value.replace(/^0*/, '');    
                }    
            });    
        };   
        //调用文本框的id 
  $("#score").numeral();  
});