controling what the user inputs in prompt

Question

hello everybody, does any one of you knows how to prevent the user from writing a string in the prompt?

Answer 1

#1:you have to clearly state in the prompt,that the user has to input something that isnt a string like a number.
#2:convert your prompt() from string to your required datatype like parseInt(prompt());
or you could just
<input type="number"/>
This forces a numeric keyboard on the user

Answer 2

You mean, something else than numbers? Cause the user always inputs a string.

Answer 3

no, I mean he have to put numbers only

Answer 4

no strings