根据javascript权威指南实现的cookie存储api哪些地方可以优化

请大家帮忙看一下下面根据javascript权威指南实现的cookie存储api哪些地方可以进行优化。
非常感谢大家的帮忙，请多多指出，谢谢。<!doctype html>
<!-- Saved from html5snippet.net -->
<html>
<head>
<meta http-equiv='Content-Type' content='text/html; charset=utf-8'/>
<style type='text/css'></style>
<script type='text/javascript'>
(function (window) {
    var iCookie = function (maxage, path) {
        return iCookie.methods._init(maxage, path);
    };
    iCookie.methods = iCookie.prototype = {
        _init: function (maxage, path) {
            this.maxage = maxage;
            this.path = path;
            this._cookie = (function () {
                var cookie = {},
                all = document.cookie;
                if (!all) {
                    return cookie;
                }
                var list = all.split("; ");
                for (var i = 0; i < list.length; i++) {
                    var c = list[i];
                    var p = c.indexOf("=");
                    var name = c.substring(0, p);
                    var value = c.substring(p + 1);
                    cookie[name] = value;
                }
                return cookie;
            } ());
            this.keys = [];
            for (var key in this._cookie) {
                this.keys.push(key);
            }
            this.length = this.keys.length;
            var that = this;
            
            return {
             getItem: function() {
                return  this.getItem.apply(that,arguments);
             },
             setItem: function() {
                return this.setItem.apply(that,arguments);
                },
             clear : function() {
                return this.clear.apply(that,arguments);
                },
            removeItem : function() {
                return this.removeItem.apply(that,arguments);
                }
              };
             
        },
        key: function (n) {
            if (n < 0 || n >= this.keys.length) {
                return null;
            }
            return this.keys[n];
        },
        getItem: function (key) {
            return this._cookie[key] || null;
        },        setItem: function (key, value) {           
            if (!(key in this._cookie)) {
                this.keys.push(key);
                this.length++;
            }
            this._cookie[key] = value;
            var cookie = key + "=" + encodeURIComponent(value);
            if (this.maxage) {
                cookie += "; max-age=" + this.maxage;
            }
            if (this.path) {
                cookie += "; path=" + this.path;
            }
            document.cookie = cookie;        },        removeItem: function (key) {
            if (!(key in this._cookie)) {
                return;
            }
            delete this._cookie[key];
            for (var i = 0; i < this.keys.length; i++) {
                if (this.keys[i] === key) {
                    this.keys.splice(i, 1);
                    break;
                }
            }
            this.length--;
            document.cookie = key + "=; max-age=0";
        },        clear: function () {
            for (var i = 0; i < this.keys.length; i++) {
                document.cookie = this.keys[i] + "=; max-age=0";
            }
            this._cookie = {};
            this.keys = [];
            this.length = 0;
        }
    };
    window.iCookie = iCookie;
} (window));window.onload = function () {    var setCookie = document.getElementById("setCookie");
    setCookie.addEventListener("click", function () {
        var myName = document.getElementById("myName");
        var myAge = document.getElementById("myAge");
        iCookie().setItem(myName.value, myAge.value);
        myName.value = "";
        myAge.value = "";
    });    var getCookie = document.getElementById("getCookie");    getCookie.addEventListener("click", function () {
        var myName = document.getElementById("myName");
        var myAge = document.getElementById("myAge");
        var age = iCookie().getItem(myName.value);
        myAge.value = age;
    });
     var clearCookie = document.getElementById("clearCookie");    
    clearCookie.addEventListener("click", function () {       
         iCookie().clear(); 
         alert("cleared.");
    });
     var removeCookie = document.getElementById("removeCookie"); 
     var myName = document.getElementById("myName");
     removeCookie.addEventListener("click", function () {       
         iCookie().removeItem(myName.value); 
         alert(myName.value + "  is removed.");
    });
    
    
};
</script>
</head>
<body><input type="text" id="myName"  />
<input type="text" id="myAge"  />
<input type="button" id="setCookie" value="SetCookie" />
<input type="button" id="getCookie" value="GetCookie" />
<input type="button" id="clearCookie" value="clearCookie" />
<input type="button" id="removeCookie" value="removeCookie" />
</body>
</html>