差异化继承

if (typeof Object.beget !== 'function') {
    Object.beget = function(o) {
        var F = function() {};
        F.prototype = o;
        return new F();
    };
}

var myMammal = {
    name: 'Herb the Mammal',
    get_name: function() {
        return this.name;
    },
    says: function() {
        return this.saying || '';
    }
};

var myCat = Object.beget(myMammal);
myCat.name = 'Henrietta';
myCat.saying = 'meow';
myCat.purr = function(n) {
    var i, s = '';
    for (i = 0; i < n; i += 1) {
        if (s) {
            s += '-';
        }
        s += 'r';
    }
    return s;
};
myCat.get_name = function() {
    return this.says + ' ' + this.name + ' ' + this.says;
};