option = {
  .....
  series: [
  {
    name: 'Punch Card',
    type: 'heatmap',
    selectedMode: false, // disable selected mode
    data: data,
    itemStyle: {
        emphasis: {
          borderColor: 'black',
          borderWidth: 2
        }
    }
}]}
var previousSelected = null;
myChart.on('click', function (params) {
  // clear previous selected
  if (previousSelected) {
    myChart.dispatchAction({
         type: 'downplay',
         seriesIndex: 0,
         dataIndex: previousSelected.dataIndex
     });
 }
  //highlight current selected
    myChart.dispatchAction({
        type: 'highlight',
        seriesIndex: 0,
        dataIndex: params.dataIndex
  });
  previousSelected = params;
});

option && myChart.setOption(option);