var $ = function(el) {
    return new _$(el);    
};
var _$ = function(el) {
    this.el = (el && el.nodeType == 1)? el: document;
};
_$.prototype = {
    constructor: this,
    addEvent: function(type, fn, capture) {
        var el = this.el;
        
        if (window.addEventListener) {
            el.addEventListener(type, fn, capture);

            var ev = document.createEvent("HTMLEvents");
            ev.initEvent(type, capture || false, false);
            // 在元素上存储创建的事件，方便自定义触发
            if (!el["ev" + type]) {
                el["ev" + type] = ev;
            }
            
        } else if (window.attachEvent) {
            el.attachEvent("on" + type, fn);    
            if (isNaN(el["cu" + type])) {
                // 自定义属性，触发事件用
                el["cu" + type] = 0; 
            }
            
            var fnEv = function(event) {
                if (event.propertyName == "cu" + type) {
                    fn.call(el);
                }
            };
            
            el.attachEvent("onpropertychange", fnEv);
            
            // 在元素上存储绑定的propertychange事件，方便删除
            if (!el["ev" + type]) {
                el["ev" + type] = [fnEv];
            } else {
                el["ev" + type].push(fnEv);    
            }
        }
        
        return this;
    },
    fireEvent: function(type) {
        var el = this.el;
        if (typeof type === "string") {
            if (document.dispatchEvent) {
                if (el["ev" + type]) {
                    el.dispatchEvent(el["ev" + type]);
                }
            } else if (document.attachEvent) {
            	// 改变对应自定义属性，触发自定义事件
                el["cu" + type]++;
            }    
        }    
        return this;
    },
    removeEvent: function(type, fn, capture) {
        var el = this.el;
        if (window.removeEventListener) {
            el.removeEventListener(type, fn, capture || false);
        } else if (document.attachEvent) {
            el.detachEvent("on" + type, fn);
            var arrEv = el["ev" + type];
            if (arrEv instanceof Array) {
                for (var i=0; i<arrEv.length; i+=1) {
                    // 删除该方法名下所有绑定的propertychange事件
                    el.detachEvent("onpropertychange", arrEv[i]);
                }
            }
        }
        return this;    
    }
};

// ------------- 以下为测试用脚本------------

var fnClick = function(e) {
    e = e || window.event;
    var target = e.target || e.srcElement;
    
    if (target.nodeType === 1) {
        alert("点击类型：" +  e.type);
        $(target).fireEvent("alert");
    }
}, funAlert1 = function() {
    alert("自定义alert事件弹出！");    
}, funAlert2 = function() {
    alert("自定义alert事件再次弹出！");    
};

// 测试用的张小姐图片
var elImage = document.getElementById("image");
$(elImage)
    .addEvent("click", fnClick)
    .addEvent("alert", funAlert1)
    .addEvent("alert", funAlert2);

// 删除自定义事件按钮
var elButton = document.getElementById("button");
$(elButton).addEvent("click", function() {
    $(elImage)
        .removeEvent("alert", funAlert1)
        .removeEvent("alert", funAlert2);    
        
    alert("清除成功！");
});