如何验证只接受第一个字母作为一个字符，并保留为一个数字在javascript中

Question

我想验证仅作为字符&剩余数字的文本框&不应该接受特殊字符。

<asp:TextBox ID="txtSlip" runat="server" CssClass="smalltextbox" PlaceHolder="Slip" Width="80px" OnKeypress="javascript:return FirstChar(event,this.value);" MaxLength="6" /> 

//First Letter Only Charactor Remaining Numbers 
function FirstChar(event) { 
var firstChar = (event.which) ? event.which : event.keyCode 
if (firstChar <= '9' && firstChar >= '0') { 
    //do your stuff 
    return true; 
} 
return true; 
} 

例如：“A00001”这样的.. 但它不为我工作..任何人的帮助，在此先感谢..

Answer 1

我发现的帮助下回答Sathiya saravana巴布回答

function FirstChar(event, val) { 
var length = val.length; 
var firstChar = (event.which) ? event.which : event.keyCode; 
if (length != 0) { 
    var firstChar = (event.which) ? event.which : event.keyCode; 
    if (firstChar >= '48' && firstChar <= '57') { 

     return true; 
    } else { 

     return false; 
    } 
} else { 

if (length == 0) { 
    var firstChar = (event.which) ? event.which : event.keyCode; 
    if ((firstChar >= '65' && firstChar <= '90') || (firstChar >= '97' && firstChar <= '122')) { 

     return true; 
    } else { 

     return false; 
    } 
    return true; 
} 
} 
} 

谢谢大家，其作品很好..

Answer 2

function FirstChar(event,val) { 
var length=val.length; 
var firstChar = (event.which) ? event.which : event.keyCode; 
if(length!=0) 
{ 

     // console.log(firstChar); 
     if (firstChar >= '48' && firstChar <= '57') { 

      return true; 
     }else 
     { 
     return false; 
     } 
}else 
{ 

     if (firstChar >= '48' && firstChar <= '57') { 

      return false; 
     }else 
     { 


     return true; 
     } 

} 
} 

Answer 3

function FirstChar(event, val) { 
    var length = val.length; 

    if (length != 0) { 
     var firstChar = (event.which) ? event.which : event.keyCode; 
     console.log(firstChar); 

     if (length != 1) { 

      if (firstChar >= '48' && firstChar <= '57') 
      { 
       return true; 
      } else 
      { 
       return false; 
      } 
     } 
     else 
     { 
      if (firstChar <= '48' && firstChar >= '57') 
      { 
       return true; 
      } else 
      { 
       return false; 
      } 
     } 
    } 
    else 
    { 
     return true; 
    } 
} 

请检查这个修改后的版本Sathiya saravana Babu回答。