Javascript:Object在使用原型时没有方法

为什么我必须调用new Chart（）从同一个类（比如说）触发一个方法？这是正确的方法吗？谢谢

  function Chart(location, startDateString, endDateString) {  

    this.location = location;
    this.startDateString = startDateString;
    this.endDateString = endDateString;
}


Chart.prototype.fnDrawStaticChart = function(chartUrl, chartData) {

    $.get(chartUrl, function() {                       
        $('#'+chartData.wrapSpecId).attr('src', chartUrl);                             
    });      
}

Chart.prototype.fnDraw = function(fnStaticChartJSON, fnStaticChartImage) {        

    $.getJSON(fnStaticChartJSON, function(data) { 

        if (data.chartData.length > 0) {    

            $('#chartDiv').append($('#template').jqote(data, '@'));       

            $.each(data.chartData, function(index, chartData) { 

                var pkgLineId = chartData.wrapSpec2.pkgLineId.pkgLineId;             
                var wrapSpecId = chartData.wrapSpecId;
                var startDate = data.startDate;
                var endDate = data.endDate;

                var chartUrl = fnStaticChartImage({
                    pkg_line_id: pkgLineId, 
                    wrap_spec_id: wrapSpecId, 
                    start_date: startDate, 
                    end_date: endDate
                });

                this.fnDrawStaticChart(chartUrl, chartData); //can't do this.  
                new Chart().fnDrawStaticChart(chartUrl, chartData); CAN do this.



            });      
    }); 
}

---

这是一个简单的范围界定问题此指向传递给$each的函数。必须将此引用的旧值存储在另一个变量中：

Chart.prototype.fnDraw = function(fnStaticChartJSON, fnStaticChartImage) {        
    var self = this;
    $.getJSON(fnStaticChartJSON, function(data) { 

        if (data.chartData.length > 0) {    

            $('#chartDiv').append($('#template').jqote(data, '@'));       

            $.each(data.chartData, function(index, chartData) { 

                var pkgLineId = chartData.wrapSpec2.pkgLineId.pkgLineId;             
                var wrapSpecId = chartData.wrapSpecId;
                var startDate = data.startDate;
                var endDate = data.endDate;

                var chartUrl = fnStaticChartImage({
                    pkg_line_id: pkgLineId, 
                    wrap_spec_id: wrapSpecId, 
                    start_date: startDate, 
                    end_date: endDate
                });

                self.fnDrawStaticChart(chartUrl, chartData);
                new Chart().fnDrawStaticChart(chartUrl, chartData);
            });      
    }); 
}

---

好的，很酷。那么为什么我不能这样称呼它。fnDrawStaticChart（）？“this”指的是$.getJSON中的某些内容吗？不，这总是指您所处函数的当前范围，在您的情况下指的是传递给$.each（）的函数（索引、图表数据）。