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Javascript IsNumeric Function

Article by:  Jeff Anderson  ( 1362 ) (2/26/2002)
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Summary: A javascript validation function to check whether the details entered by a user are numeric.
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The simplest way to check whether the details entered in a text field are numeric is to to loop through the string and compare each character to a pre-defined list of acceptable characters.

In this function, we've allowed decimal points and numbers nought through 9.

We use two methods to help us here : the charAt and indexOf.

Using the charAt method, we can find out which character is filling a designated position within a string. We then use the indexOf method to search our ValidChars list of valid characters. If it doesn't exist, (if ValidChars.indexOf(Char) == -1) this means the user has entered an invalid character. Here's the full function.



function IsNumeric(sText)
{    var ValidChars = "0123456789.";    var IsNumber=true;    var Char;    for (i = 0; i < sText.length && IsNumber == true; i++)       {       Char = sText.charAt(i);       if (ValidChars.indexOf(Char) == -1)          {          IsNumber = false;          }       }    return IsNumber;    }

To understand how to use the IsNumeric function to validate a form, see Form Validation function Page.







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