如何使用外部Json值处理AngularJs图表

Question

我需要创建一个带有外部JSON数据的图表js，这里我尝试使用Aungularjs中的chartjs

<script>

                            var barChartData = {
        labels: ["January", "February", "March", "April", "May", "June", "July"],
        datasets: [{
            label: 'Dataset 1',
            backgroundColor: "#09a",
          data: ["100", "150", "50", "120", "75", "250", "31"],
        }]

    };

    window.onload = function() {
        var ctx = document.getElementById("canvas").getContext("2d");
        window.myBar = new Chart(ctx, {
            type: 'bar',
            data: barChartData,
        });

    };


</script>

此处JSON在内部使用变量 barChartData 处理并分配给数据：barChartData ，如何对外部JSON执行相同操作？