iframe窗口事件监听

var IframeOnClick = {  
    resolution: 200,  
    iframes: [],  
    interval: null,  
    Iframe: function() {  
        this.element = arguments[0];  
        this.cb = arguments[1];   
        this.hasTracked = false;  
    },  
    track: function(element, cb) {  
        this.iframes.push(new this.Iframe(element, cb));  
        if (!this.interval) {  
            var _this = this;  
            this.interval = setInterval(function() { _this.checkClick(); }, this.resolution);  
        }  
    },  
    checkClick: function() {  
        if (document.activeElement) {  
            var activeElement = document.activeElement;  
            for (var i in this.iframes) {  
                if (activeElement === this.iframes[i].element) { // user is in this Iframe  
                    if (this.iframes[i].hasTracked == false) {   
                        this.iframes[i].cb.apply(window, []);   
                        this.iframes[i].hasTracked = true;  
                    }  
                } else {  
                    this.iframes[i].hasTracked = false;  
                }  
            }  
        }  
    }  
}; 
//调用
var ifs = document.getElementsByClassName("iframe");

for(var i = 0; i < 12; i ++) {
    IframeOnClick.track(ifs[i], function() { alert('a click'); });  
}