How to achieve only selecting the current item in VChart when clicking on the legend?

Question title

How to implement VChart to only select the current item when clicking on a legend?

Problem description

When clicking on the legend, can you change to select the current item and not select other items?

Solution

VChart supports configuring legend selection mode, including single selection mode

legends: {
    orient: 'right',
    selectMode: 'single', // Configure legend selection mode
    defaultSelected: ['Type D'],
    title: {
      visible: true,
      text: 'Single Select'
    }
  }

Code example

const data = [
  {
    name: 'Type A',
    value: 33934,
    year: 2010
  },
  {
    name: 'Type A',
    value: 52503,
    year: 2011
  },
  {
    name: 'Type A',
    value: 57177,
    year: 2012
  },
  {
    name: 'Type A',
    value: 69658,
    year: 2013
  },
  {
    name: 'Type A',
    value: 97031,
    year: 2014
  },
  {
    name: 'Type A',
    value: 119931,
    year: 2015
  },
  {
    name: 'Type A',
    value: 137133,
    year: 2016
  },
  {
    name: 'Type A',
    value: 154175,
    year: 2017
  },
  {
    name: 'Type B',
    value: 24916,
    year: 2010
  },
  {
    name: 'Type B',
    value: 24064,
    year: 2011
  },
  {
    name: 'Type B',
    value: 29742,
    year: 2012
  },
  {
    name: 'Type B',
    value: 29851,
    year: 2013
  },
  {
    name: 'Type B',
    value: 32490,
    year: 2014
  },
  {
    name: 'Type B',
    value: 30282,
    year: 2015
  },
  {
    name: 'Type B',
    value: 38121,
    year: 2016
  },
  {
    name: 'Type B',
    value: 40434,
    year: 2017
  },
  {
    name: 'Type C',
    value: 11744,
    year: 2010
  },
  {
    name: 'Type C',
    value: 17722,
    year: 2011
  },
  {
    name: 'Type C',
    value: 16005,
    year: 2012
  },
  {
    name: 'Type C',
    value: 19771,
    year: 2013
  },
  {
    name: 'Type C',
    value: 20185,
    year: 2014
  },
  {
    name: 'Type C',
    value: 24377,
    year: 2015
  },
  {
    name: 'Type C',
    value: 32147,
    year: 2016
  },
  {
    name: 'Type C',
    value: 39389,
    year: 2017
  },
  {
    name: 'Type D',
    value: null,
    year: 2010
  },
  {
    name: 'Type D',
    value: null,
    year: 2011
  },
  {
    name: 'Type D',
    value: 7988,
    year: 2012
  },
  {
    name: 'Type D',
    value: 12169,
    year: 2013
  },
  {
    name: 'Type D',
    value: 15112,
    year: 2014
  },
  {
    name: 'Type D',
    value: 22452,
    year: 2015
  },
  {
    name: 'Type D',
    value: 34400,
    year: 2016
  },
  {
    name: 'Type D',
    value: 34227,
    year: 2017
  },
  {
    name: 'Other',
    value: 12908,
    year: 2010
  },
  {
    name: 'Other',
    value: 5948,
    year: 2011
  },
  {
    name: 'Other',
    value: 8105,
    year: 2012
  },
  {
    name: 'Other',
    value: 11248,
    year: 2013
  },
  {
    name: 'Other',
    value: 8989,
    year: 2014
  },
  {
    name: 'Other',
    value: 11816,
    year: 2015
  },
  {
    name: 'Other',
    value: 18274,
    year: 2016
  },
  {
    name: 'Other',
    value: 18111,
    year: 2017
  }
];
const spec = {
  type: 'line',
  data: [
    {
      id: 'line',
      values: data
    }
  ],
  xField: 'year',
  yField: 'value',
  seriesField: 'name',
  legends: {
    orient: 'right',
    selectMode: 'single', // Configure legend selection mode
    defaultSelected: ['Type D'],
    title: {
      visible: true,
      text: 'Single Select'
    }
  },
  axes: [
    {
      orient: 'left',
      label: {
        inside: true,
        space: 2,
        style: {
          textBaseline: 'bottom',
          textAlign: 'start',
          fontWeight: 'bold'
        }
      },
      tick: {
        visible: false
      },
      domainLine: {
        visible: false
      },
      title: {
        visible: true,
        text: 'Axis Title'
      }
    }
  ]
};

const vchart = new VChart(spec, { dom: CONTAINER_ID });
vchart.renderSync();

// Just for the convenience of console debugging, DO NOT COPY!
window['vchart'] = vchart;