函数化2

var mammal = function(spec) {
        var that = {};

        that.get_name = function() {
            return spec.name;
        };

        that.says = function() {
            return spec.saying || '';
        };
        return that;
    };

var myMammal = mammal({
    name: 'Herb'
});

//构造器函数Cat
var cat = function(spec) {
        spec.saying = spec.saying || 'meow';
        var that = mammal(spec);
        that.purr = function(n) {
            var i, s = '';
            for (i = 0; i < n; i += 1) {
                if (s) {
                    s += '-';
                }
                s += 'r';
            }
            return s;
        };
        that.get_name = function() {
            return that.says() + ' ' + spec.name + ' ' + that.says();
        };
        return that;
    };

var myCat = cat({
    name: 'Henrietta'
});
console.log(myCat.get_name());