How to disable/enable keys

We would like to learn how to disable/enable keys for within a text box, with coding as simple as possible.

For example in a text box that provides a decimal measurement we would only want numbers 0-9 & period (.) & backspace to be enabled & all other keys disabled.

For simplicity is it possible to disable all keys then enable (0-9 . backspece) rather than individually disable all the others?

Another example would be to enable only a-z lower case.

Or A-Z upper case & maybe some others like @, #, $, %, &.

Another idea we have is to disable these characters < > { } [ ] from all text boxes & text areas, and also record the users ID, together with a warning message, of whoever attempts to insert those characters.

We are familiar with the Javascript Char Codes (Key Codes) but wonder if the numbers are consistent.
https://www.cambiaresearch.com/articles/...-key-codes

I tried this coding but it didnt work, however we would like someting similar;

PHP Code:

<script>
function accept_numeric_only(e) {
e = e || window.event;
var k = e.keyCode || e.which;
var upperlowercase = e.shiftKey;
if(uppercase && lowercase && k <= 7 && k >= 9 && k <= 47 && k >= 58 && k <= 189 && k >= 191) {
document.getElementById("error").style.display = "inline";
return false; }
document.getElementById("error").style.display = "none";
return true; }
function init() {
document.getElementById("length, width, height, diameter, weight, quantity, price").onkeydown = accept_numeric_only; } //These are the text boxes to be disabled
</script> 


Please dont tell us to try HTML coz that doesnt work properly.

In addition to disabling keys, is it possible to disallow by form_validation?

Has anybody any answers or ideas?