Javascript IsNumeric Function

Why go thru the trouble of writing your own function? isNaN works just fine for the same purpose! it will return true for stuff like 20a, a20, 20.a, 20a. and etc. it will return false for 20, 20.1 and any other number. It work in IE as far as I know.

Hey anton thanks, this is exactly what I was looking for. I‹m glad I didn‹t use the function above :)

Esta muy buena esa funcion esjusto lo que necesitaba

Anton is right on the money. Thanks.

What about negetive numbers. isNAN wont return right results. This function by adding minus (-) in the list return true.

Great...

What if the user enters multiple '.'?

Just added negative value....

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 ((i == 0) && (Char == "-")) // check first character for minus sign
continue;
if (ValidChars.indexOf(Char) == -1)
{
IsNumber = false;
}
}
return IsNumber;

}

Didnt test it...please reply if u find any error....
By the way ... isNaN function does not apply when u need strict numeric validation.... for example:
'2a5' returns false (2 will be the numeric value) which should not be since the actual value intended was 25... the character 'a' accidentally typed.... get the point??

When I tried '2a5', I got true...

You don't need de IsNumeric variable, you can return true or false in the first instance when you got a no numeric character, this is the my change:

function IsNumeric(sText)
{
var ValidChars = "0123456789.";
var Char;


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

}

There is a simple way to it.

Javascript has an inbuilt isNaN function to check numbers.

Please refer "http://developer.netscape.com/docs/manuals/js/core/jsguide15/fcns.html"

You should check for the empty string or you will assume the input is correct, this is clearly not right

if (isNaN(form.field1.value)) {
alert('Please enter only numerical values into Field 1.');
}

Does the same thing!

You folks are using isNaN() incorrectly. You are getting the results you are seeing through pure serendipity. isNaN() is used to detect whether a number gets set to the value NaN (which is defined a 'not a number' - a designation similar to 'infinity', which isn't a number but defines something specific). In other words, check this site:

http://www.thedance.net/~roth/JAVASCRIPT/refp_268.htm

Thanks John that was a good solution much easier then writing the whole Function out! This is what programming is about.

I would change the code with Not a Number like this.

if (isNaN(pareseFloat(form.field1.value))) {
alert('Please enter only numerical values into Field 1.');
}

Use pareseInt if you don't need floating value

You shall remove the 'e' from the word 'parese', because the form validation prohibits the word 'parese' without the e :s

IsNumeric() did a good job for me
keep it up guys

I have used the function above and it hang the entire IE. I would not recommend on using it. Use isNaN instead it works just fine.

Yeah, I looked at that site and it said isNan() is used to check if something was a valid number. So i'll stick with isNaN(). Nice function though :).

I'm looking for a function to validate a phone number. I was going to adapt the IsNumeric function to do this, but I can't get this to work at all even in the way it's written. I've copied it exactly using the validate function to call it. I'm I missing something?

i can't believe all the odd ways i've read people try to sort this problem out!
Regular Expressions are the way to go when you need to check string contents.

myRegExp = /[0-9]+/g
myNumber = new String("93932")

if(myRegExp.test(myNumber))
{
there are numbers in myNumber
}
else
{
there are no numbers in myNumber
}

the cool thing about regular expressions is that you can do pattern matching too, not just a binary check for a condition.

ie. you could validate a phone number with the following patter:

myRegExpPhoneNumber = /(\d\d\d) \d\d\d-\d\d\d\d/

\d is a number 0 through to 9. So if you test (234) 983-8282 against it, it will return true, anything else will be false. Perfect. none of this isNan garbage.

If you want to validate against a string containing only numbers, the expression is:

^-{0,1}\d*\.{0,1}\d+$

^ == beginning of line
-{0,1} == 0 or 1 minus signs
\d* == 0 or more digits
\.{0,1} == 0 or 1 decimal points
\d == 1 or more digits
$ == end of line

You should never have multiple returns in any function!!!!!

The last comment about multiple returns from function/method is BS!

if you have something like this

if(flag) {
Do some code...
} else {
showmessage;
}

looks better like this...


if(!flag) {
showmessage;
return;
}

do some code...

since it cuts down on the ammount of nessted code and its easier to read. It stems from machine code programming many moons ago when having more than one return statement really did send your head into overload!! In this day just use common sense!

the isNaN function does not work properly for this type of validation

the value 3a3 returns false (ie will not be picked up by the above validation functions using isNan)

i think reg expressions are the way to go for this