SO Answer: javascript regex to disallow all special characters

See: http://stackoverflow.com/questions/15243387/javascript-regex-to-disallow-all-special-characters

HTML

<input type="text" id="validate" />
<div id="x"></div>

JavaScript

Array.prototype.indexOf = Array.prototype.indexOf || function (searchElement) {
        "use strict";
        if (this == null) {
            throw new TypeError();
        }
        var t = Object(this);
        var len = t.length >>> 0;
        if (len === 0) {
            return -1;
        }
        var n = 0;
        if (arguments.length > 1) {
            n = Number(arguments[1]);
            if (n != n) { // shortcut for verifying if it's NaN
                n = 0;
            } else if (n != 0 && n != Infinity && n != -Infinity) {
                n = (n > 0 || -1) * Math.floor(Math.abs(n));
            }
        }
        if (n >= len) {
            return -1;
        }
        var k = n >= 0 ? n : Math.max(len - Math.abs(n), 0);
        for (; k < len; k++) {
            if (k in t && t[k] === searchElement) {
                return k;
            }
        }
        return -1;
}

document.querySelector('#validate').onkeypress = validate;

function validate(e) {
            e = e || event;
            return /[a-z0-9]/i.test(String.fromCharCode(e.charCode || e.keyCode)) 
                    || !!(!e.charCode && ~[8,37,39,46].indexOf(e.keyCode));
}