making variable a number

Question

I have a text box that I want a person to add a number, and only a number into. How would I make a function that, if the value added to the text box was not a number, they would get an alert that said, "must add a number", or something similar. without using RegEx!

thanks!

http://stackoverflow.com/questions/175739/is-there-a-built-in-way-in-javascript-to-check-if-a-string-is-a-valid-number — Paolo Moretti, Jan 08 '16 at 19:40
do you want to perform this check when they submit the form, or when they're entering text? I'm using jquery for something similar, when the user clicks the submit button. — luke_mclachlan, Jan 08 '16 at 19:41

score 4 · Accepted Answer · answered Jan 08 '16 at 19:39

4

http://www.w3schools.com/tags/att_input_type.asp

You want to use type="number" on your input field

Type a number:
<input type="number"/>

answered Jan 08 '16 at 19:39

neaumusic

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And if you want to include decimal, you can use step="0.01", or step="any" – CodeLikeBeaker Jan 08 '16 at 19:43

score 2 · Answer 2 · answered Jan 08 '16 at 19:42

2

Here is a solution that you can use to only allow the user to enter numbers, they can´t add anything that´s not a number

<HTML>
   <HEAD>
   <SCRIPT language=Javascript>
      function isNumberKey(evt)
      {
         var charCode = (evt.which) ? evt.which : event.keyCode
         if (charCode > 31 && (charCode < 48 || charCode > 57))
            return false;

         return true;
      }
   </SCRIPT>
   </HEAD>
   <BODY>
      <INPUT id="txtChar" onkeypress="return isNumberKey(event)" type="text" name="txtChar">
   </BODY>
</HTML>

answered Jan 08 '16 at 19:42

Rashwan L

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what does charCode check? did you get this from somewhere? thanks – neaumusic Jan 08 '16 at 19:44
The charCode property returns the Unicode character code of the key that triggered the onkeypress event. – Rashwan L Jan 08 '16 at 19:44
you might need to check keypad numbers (probably not), and i think mac and windows might have slightly different codes for 0 too – neaumusic Jan 08 '16 at 19:46
1

@neaumusic this works on PC and Mac and so does 0 just tried. – Rashwan L Jan 08 '16 at 19:48
alright sorry for bothering you then, you could also use `!isNaN(Number(inputValue))` – neaumusic Jan 08 '16 at 19:51

making variable a number

2 Answers2