How to prevent users from entering invalid characters inside an input field

Question

Given a text input field. How can I prevent users from entering spaces, and other other than letters numbers or dashes (-).

Alphanumerics only - \"The alphanumeric

Answer 1

Though my answer is very late, but this may help for further readers/techie's. Who wants to implement a textbox to accepts with below condition.

• should accept Alphabets.
• should accept Numbers.
• should not accept any special characters.

Below is the code.

$("input[name='txtExample'] ").focus(function (e) {
		if (!(e.which != 8 && e.which != 0 && ((e.which >= 48 && e.which <= 57)  || (e.which >= 65 && e.which <= 90) || (e.which >= 97 && e.which <= 122) ))) {
			event.preventDefault();
		}
	}).keyup(function (e) {
		if (!(e.which != 8 && e.which != 0 && ((e.which >= 48 && e.which <= 57)  || (e.which >= 65 && e.which <= 90) || (e.which >= 97 && e.which <= 122) ))) {
		event.preventDefault();
			}
	}).keypress(function (e) {
		if (!(e.which != 8 && e.which != 0 && ((e.which >= 48 && e.which <= 57)  || (e.which >= 65 && e.which <= 90) || (e.which >= 97 && e.which <= 122) ))) {
			event.preventDefault();
		}
	
	});

added with example.