How to use the echarts.getInstanceByDom function in echarts

getEchartsInstance() {
    // return the echart object
    return echarts.getInstanceByDom(this.refs.echartsDom) || echarts.init(this.refs.echartsDom, this.props.theme)
  }

getEchartsInstance() {
    // return the echart object
    const me = this;
    const props = me.props;
    const option = props.option;
    const theme = props.theme || option.theme;
    return echarts.getInstanceByDom(me.wrapper) || echarts.init(me.wrapper, theme);
  }

renderEChart = () => {
    let chartObj =
            echarts.getInstanceByDom(this.refs.chart) ||
            echarts.init(this.refs.chart, this.props.theme);
    if (this.props.showLoading) {
      chartObj.showLoading();
    }
    chartObj.setOption(this.props.options);
    chartObj.hideLoading();
    return chartObj;
  }
  render() {

getEchartsInstance = () => {
    if(_.isNil(this.refs.echartsDom)) {
      return null
    }
    return echarts.getInstanceByDom(this.refs.echartsDom) || echarts.init(this.refs.echartsDom, this.props.theme)
  }

drawChart() {
    const chart = echarts.getInstanceByDom(this.container);
    if (!chart) {
      this.chart = echarts.init(this.container);
    }

    this.chart.showLoading();
    this.loadData().then(data => {
        this.chart.hideLoading();
        this.renderChart(data);
    }, 3000);
  }