Block Number in text field using JavaScript

In this article, I will demonstrate how to allow user to input block numeric characters in a TextBox field by using Javascript. The program prevents user from copying and pasting numerical characters into the TextBox.

// Restrict user input in a text field
// create as many regular expressions here as you need:
var digitsOnly = /[1234567890]/g;
var integerOnly = /[0-9.]/g;
var alphaOnly = /[A-Za-z]/g;
var usernameOnly = /[0-9A-Za-z._-]/g;

function restrictInput(myfield, e, restrictionType, checkdot){
if (!e) var e = window.event
if (e.keyCode) code = e.keyCode;
else if (e.which) code = e.which;
var character = String.fromCharCode(code);

// if user pressed esc… remove focus from field…
if (code==27) { this.blur(); return false; }

// ignore if the user presses other keys
// strange because code: 39 is the down key AND ‘ key…
// and DEL also equals .
if (!e.ctrlKey && code!=9 && code!=8 && code!=36 && code!=37 && code!=38 && (code!=39 || (code==39 && character==”‘”)) && code!=40) {
if (character.match(restrictionType)) {
if(checkdot == “checkdot”){
return !isNaN(myfield.value.toString() + character);
} else {
return true;
}
} else {
return false;
}
}
}