var patron1 = /[A-Z]/, 

    patron2 = /\d/,

    patron3 = /[A-Z]{1}\d{3}/gi,

    caracter;

​

document.querySelector("#foo").addEventListener("keypress", function(event){

    caracter = String.fromCharCode(event.keyCode);

    if ((patron3.test(this.value) && this.value.length == 4) || this.value.length == 4){

        this.value += "-";

    }

    if ((!this.value.length && !patron1.test(caracter)) || 

        (patron1.test(this.value) && !patron2.test(caracter)) || 

        this.value.length == 16){

        event.preventDefault();

    }

}, false);