JS can only enter a number (positive integer, positive, negative, decimal)

JS can only enter a number (positive integer, positive, negative, decimal)
This is a simple use of JS to verify that you can only enter a number (positive integer, positive, negative, decimal) Oh, if you are considering allowing users to enter numbers can come in and see.
Only numeric regular validation

<script language= "Web Effects" type= "Text/javascript" >
function Checknum (obj)
{
var re =/^-? [1-9]* (. d*) $|^-?0 (. d*)? $/;
if (!re.test (Obj.value))
{
Alert ("illegal number");
Obj.value= "";
Obj.focus ();
return false;
}
}
</script>
<input name= "rate" type= "text" onkeyup= "Checknum (This)"/>

The Validation text box in contains only integers and can be entered, positive and negative integers, and other characters cannot be entered
Use this code to solve the problem
var flag3 = false;
var planallocation = document.getelementsbyname (' planallocation_xx '); Planned allocation
var size1 = planallocation.length;
var exp =/^ (-?[ 1-9][0-9]*|0) $/;
Determines the number of planned entries entered is an exception character
for (Var i=0;i<size1;i++)
{
if (!exp.test (Planallocation[i].value))
{
Flag3 = true;
break;
}
}

if (flag3==true)
{
Alert ("Please input integer, cannot contain special characters");
return false;
}

Can only be digital isNaN

<script language= "javascript" type= "Text/javascript"
function checknum (obj)
{
 var re =/^-?[ 1-9]* (. d*)? $|^-?d^ (. d*) $/;
     if (!re.test (obj.value)
    {
if (isNaN (obj.value)) {         alert ("illegal numbers");
  obj.value= "";
        Obj.focus ();
        return false;}
    }
} 
</script><input name= "rate" type= "text" onkeyup= "Checknum (This)"/>