JS 判断为0或空或字母时不能输入

onkeyup=\"return checknum(this)\"

 //判断为0或空或字母时不能输入
     function checknum(obj) {
        var flagId = obj.id;
        var price = obj.value;
        if (price == "" || price == "0") {
            obj.value = 0;
        }
        if (price == "" || price == "0")
            obj.value = 0;
        else if (isNaN(price)) {
            obj.value = 0;
        }
     }

只能输入中文英文数字

/[^\a-\z\A-\Z0-9\u4E00-\u9FA5]/g