D3给柱形图添加hover

重点代码块：

const svg: any = d3.select(this.$refs[ref])
      .attr('width', this.width)
      .attr('height', this.height);
    svg.append('g')
      .selectAll('rect')
      .data(data)
      .join('rect')
      .attr('x', (d: any, i: number) => x(i))
      .attr('y', (d: any) => y(d.value))
      .attr('height', (d: any) => y(0) - y(d.value))
      .attr('fill', (d: any, i: number) => {
     
        if (difColor) {
     
          return this.colorArr[i];
        }
        return this.colorArr[1];
      })
      .attr('width', x.bandwidth())
      .on('mouseover', (data: any, index: any) => {
     
        svg.append('text')
          .attr('font-family', 'sans-serif')
          .attr('font-size', 10)
          .attr('text-anchor', 'middle')
          .attr('class', 'divergence')
          .attr('x', x(index)) // x轴对应的位置
          .attr('y', y(data.value)) // y轴对应的位置
          .attr('dx', '8px')
          .text(data.value);
      })
      .on('mouseout', () => {
     
        d3.selectAll('.divergence').remove();
      });

参考地址：
https://wiki.jikexueyuan.com/project/d3wiki/interactive.html
https://observablehq.com/@d3/horizontal-bar-chart
https://observablehq.com/@d3/diverging-bar-chart