validating user input

hosefo81 · March 1st, 2004, 09:54 AM

i want to check if user enter a string in the textbox but the code below has error.
Please help me correct it.

<html>
<head>
    <title>Testing</title>
    <style>
        #textbox {position:absolute; left:200px};
    </style>
    <script>
        function validate(textbox)
        {
            if(isNumber(textbox.value))
            {
                alert("Please enter string");
                textbox.select();
                textbox.focus();
            }
        }
    </script>
</head>
<body onload="document.myform.custfname.select(); document.myform.custfname.focus();">
<form name="myform" >

Customer First Name <input id="textbox" type="text" name="custfname"><br><br>

<input type="button" value="Submit" onclick="validate(myform.custfname)">

</form>
</body>
</html>

pgtips · March 1st, 2004, 10:14 AM

There is no javascript function called <s>isNumeric</s>isNumber. I would use a regular expression for this:

Code:

function validate(textbox)
{
    if ( /[^a-zA-Z]/.test(textbox.value) )
    {
         alert("Please enter string");
         textbox.select();
         textbox.focus();
    }
}

hth
Phil

joefawcett · March 1st, 2004, 10:15 AM

What is the error?
What does your isNumber function look like and what do you want it to do?
Do you want to test to see if it is a valid number or just contains digits?

Also there is no point selecting and then focusing. Select highlights all the text, focus just puts the caret in the text box at position one.

--

Joe

hosefo81 · March 1st, 2004, 11:34 AM

The status bar display error and nothing happens when i clicked the button.Well, i learn on a book of javascript that i can check whether the user enter digit in the textbox.The select()and focus() function is also from the book that say it use together to highlight a desired textbox.

Actually what i want to do is to test if the value entered is digit. Because i have a few textbox and i want to test if the user entered valid value.For example, if a textbox requires digit and the user entered string, then i would like to select the textbox to let the user enter it.
And how can i check if it is a string? what's the function?
Could you please show me by adding how to test is a digit and test is a string in the textbox?

Snib · March 1st, 2004, 02:01 PM

Use typeof():

alert(typeof variable);

HTH,

----------
---Snib---
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joefawcett · March 2nd, 2004, 05:35 AM

This should test for a numeric value:

Code:

function isNumeric(Value)
{
  var oRE = /^[-+]?(\d*\.)?\d+([eEdD][-+]?\d+)?$/;
  return oRE.test(Value);
}

You may just want integer values though.

--

Joe

hosefo81 · March 3rd, 2004, 07:53 AM

Thanks guys. i finally make it. joefawcett's function does'nt work for me. but thanks for helping anywhere.Here's the code that work for me.
<html>
<head>
    <title>Testing</title>
    <style>
        #textbox {position:absolute; left:200px};
    </style>
    <script>
    function isDigit (c)
    {
            return ((c >= "0") && (c <= "9"))
    }

    function validate(obj)
    {
           value = obj.value;
            for (n = 0; n < value.length; n++)
               if ( !isDigit(value.charAt(n)))
         {
            obj.select();
                 obj.focus();
                 alert("Field must be numeric");
                   return;

               }
    }
    function valid(textbox)
    {
          if ( /[^a-zA-Z]/.test(textbox.value) )
            {
                 alert("Please enter string");
                 textbox.select();
                 textbox.focus();
            }
    }

</script>
</head>
<body onload="document.myform.custfname.select(); document.myform.custfname.focus();">
<form name="myform" >
Telephone No. <input id="textbox" type="text" name="custfname" onBlur="validate(this);"><br><br>

Customer Last Name <input id="textbox" type="text" name="custlname" onBlur="valid(this);"><br><br>

<input type="button" value="Submit" > <br><br>
</form>
</body>
</html>

pgtips · March 3rd, 2004, 08:09 AM

If you just wanted to allow integers only in your telephone number field you could use a simple regexp in your validate() function, like this:

Code:

    function validate(obj) 
    {
          if ( /[^0-9]/.test(obj.value) )
            {
                 alert("Field must be numeric.");
                 obj.select();
                 obj.focus();
            }
    }

joefawcett · March 3rd, 2004, 08:19 AM

Quote:

quote:Originally posted by hosefo81
Thanks guys. i finally make it. joefawcett's function does'nt work for me.

Tried this code and it works fine, if you'd said you wanted to check for a phone number I'd have made it simpler, originally you said you were checking the customer's forename...
[code]
function isNumeric(Value)
{
var oRE = /^[-+]?(\d*\.)?\d+([eEdD][-+]?\d+)?$/;
return oRE.test(Value);
}

function testValidator(arrTest)
{
  var sResult = "";
  for (var i = 0; i < arrTest.length; i++)
  {
    var sTest = arrTest[i];
    sResult += sTest + " => " + isNumeric(sTest) + "\n";
  }
  alert(sResult);
}

testValidator(["0123456", "123a456", "0.123", "-1.1234", "-123456", "-.12345", "123.45E2"]);

[code]

--

Joe

joefawcett · March 3rd, 2004, 08:21 AM

Quote:

quote:Originally posted by pgtips
There is no javascript function called <s>isNumeric</s>isNumber. I would use a regular expression for this:

Code:

function validate(textbox)
{
    if ( /[^a-zA-Z]/.test(textbox.value) )
    {
         alert("Please enter string");
         textbox.select();
         textbox.focus();
    }
}

hth
Phil

As a side issue this sort of regular expression doesn't cope well with characters that have diacritical marls etc.

--

Joe