I've created a vertical stacked bar chart with Baidu ECharts.
Is it possible to show the sum of all values on top of the stack?
Edited : i have edited my example using the (very well explained) answer from @jeffrey but i get Uncaught TypeError: Cannot read property 'forEach' of undefined error. What am i doing wrong here ?
<!DOCTYPE html>
<html style="height: 100%">
   <head>
       <meta charset="utf-8">
   </head>
   <body style="height: 100%; margin: 0">
       <div id="container" style="height: 100%"></div>
       <script type="text/javascript" src="echarts-en.min.js"></script>
       <script type="text/javascript">
var     mySeries = [
            {
                name: 'Department 1',
                type: 'bar',
                stack: 'stack1',
                data: [320, 302, 301, 334, 390, 330, 320]
            },
            {
                name: 'Department 2',
                type: 'bar',
                stack: 'stack1',
                data: [120, 132, 101, 134, 90, 230, 210]
            },
            {
                name: 'Department 3',
                type: 'bar',
                stack: 'stack1',
                data: [220, 182, 191, 234, 290, 330, 310]
            },
            {
                name: 'Department 4',
                type: 'bar',
                stack: 'stack1',
                data: [150, 212, 201, 154, 190, 330, 410]
            },
            {
                name: 'Department 5',
                type: 'bar',
                stack: 'stack1',
                data: [185, 120, 55, 66, 77, 88, 40],
                label: {
                            normal: {
                                show: true,
                                position: 'top',
                                formatter: (params) => {
                                    let total = 0;
                                    this.series.forEach(serie => {
                                       total += serie.data[params.dataIndex];
                                    })
                                    return total;
                                }
                            }
                        }
            }
        ];
        var dom = document.getElementById("container");
        var myChart = echarts.init(dom);
        var option = null;
        option = {
            tooltip : {
                trigger: 'axis',
                axisPointer : {        
                    type : 'shadow'       
                }
            },
            legend: {
                data: ['Department 1', 'Department 2','Department 3','Department 4','Department 5'],
            },
            toolbox: {
                show: true,
                orient: 'vertical',
                left: 'right',
                top: 'center',
                feature: {
                    dataView: {show: false, readOnly: false},
                    magicType: {show: true, type: ['line', 'bar', 'stack', 'tiled']},
                    restore: {show: true},
                    saveAsImage: {show: true}
                }
            },
            grid: {
                left: '3%',
                right: '4%',
                bottom: '3%',
                containLabel: true
            },
            yAxis:  {
                type: 'value'
            },
            xAxis: {
                type: 'category',
                data: ["Jen\n2018", "Feb\n2018", "Mar\n2018", "Apr\n2018", "May\n2018", "Jun\n2018", "Jul\n2018"]
            }
        };;
        myChart.setOption(option, true);
        myChart.setOption({
            series: mySeries
        })
        </script>
   </body>
</html> 
 
     
    