Validate input text field to number with two decimal places

HTML:

<input type="text" id="inputfieldid" maxlength="10"

onkeydown="ValidateInputNumber(this.value);"  onkeyup=" ValidateInputNumber(this.value);" onchange=" ValidateInputNumber(this.value);" />

Javascript:

 function ValidateInputNumber(input){

//You can specify any reg ex here to validate

 var pattern = new RegExp(/^[0-9]*(\.[0-9]?[0-9]?)?$/);

 var resultvalue = pattern.test(input);

 if(!resultvalue)

   {

     var inputlength = input.length;

     input = input.substring(0, inputlength-1);

     $('#inputfieldid').val(input);

    }

 }