Maybe this is not for this Forum... Maybe for the JavaScript, Web ClientSide-programing or something else.
Why not use the

parseInt()
//or
parseFloat()

functions and the convert the number

number.toString

and compare the both Strings
if equal then it is OK
if not - the text is not a number
Note that you can get NaN result from parseFloat()
Hope this helps.
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btw. I have send of photo of me to you some time ago, it was shown for some time, but it is lost now...
Any ideas?