Script for allow just a defined string of chars

soloPermitir.js

    var soloPermitir = function (a){
        // console.dir($(this).data('permitido'));
        // console.dir(a.data);
        var permitido = ($(this).data('permitido') || a.data.permitido).toString();
        var c=a.which,
            d=a.keyCode,
            e=String.fromCharCode(c).toLowerCase(),
            f=permitido;

            (-1!=f.indexOf(e)||9==d||37!=c&&37==d||39==d&&39!=c||8==d||46==d&&46!=c)&&161!=c||a.preventDefault();
    };

    $.fn.soloPermitir = function(b){
        $(this).on('keypress', {permitido: b}, soloPermitir);
        return $(this);
    };