Keep prototype

gistfile1.js

var prototypeEmployed = {
    toString: function () {
        return "Name:" + this.name + ", Salary:" + this.salary;
    }
};

function newEmployed(name, salary) {
    var employed = Object.create(prototypeEmployed);
    employed.name = name;
    employed.salary = salary;
    return employed;
}

prototypeEmployed.getCategory = function () {
    return this.salary > 800 ? "Superior" : "Normal";
}

var joe= newEmployed("Jose", "10");
console.log("Joe ",joe.getCategory());

var walter= newEmployed("Walter", "100000");
console.log("Walter ",walter.getCategory());