d3.js + React，node.getBoundingClientRect 不是函数

Question

我正在使用 D3 在 React 中制作折线图，并且当将鼠标悬停在包含当前数据点的数据的图表内时，我尝试显示工具提示。图表渲染正确，但是当我将鼠标悬停在其中时，我收到错误node.getBoundingClientRect is not a function。

我正在关注这个示例，它没有使用 React，那么它是否与 React 处理事物的方式有关？

这就是我的组件的样子：

class LineChart extends Component {

    wrapper = React.createRef();

  componentDidMount() {
    const {data} = this.props

    let svg = d3.select("body svg.mySvg"),
      margin = {top: 20, right: 20, bottom: 30, left: 40},
      width = +svg.attr("width") - margin.left - margin.right,
      height = +svg.attr("height") - margin.top - margin.bottom;

    const parseTime = d3.timeParse("%Y")
    const bisectDate = d3.bisector(function(d) { return d.year; }).left;

    const x = d3.scaleTime().range([0, width]);
    const y = d3.scaleLinear().range([height, 0]);

    const line = d3.line()
      .x(function(d) { return x(d.year); })
      .y(function(d) { return y(d.value); });

    let g = svg.append("g")
      .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

    data.forEach(function(d) {
      d.year = parseTime(d.year);
      d.value = +d.value;
    });

    x.domain(d3.extent(data, function(d) { return d.year; }));
    y.domain([0, d3.max(data, function(d) { return d.value; })]);

    g.append("g")
        .attr("class", "axis axis--x")
        .attr("transform", "translate(0," + height + ")")
        .style("color", "#fff")
        .call(d3.axisBottom(x));

    g.append("g")
        .attr("class", "axis axis--y")
        .style("color", "#fff")
        .call(d3.axisLeft(y).ticks(7).tickFormat(function(d) { return d; }))

    g.append("path")
        .datum(data)
        .attr("class", "line")
        .attr("d", line);

    let focus = g.append("g")
        .attr("class", "focus")
        .style("display", "none");

    focus.append("line")
        .attr("class", "x-hover-line hover-line")
        .attr("y1", 0)
        .attr("y2", height);

    focus.append("line")
        .attr("class", "y-hover-line hover-line")
        .attr("x1", width)
        .attr("x2", width);

    focus.append("circle")
        .attr("r", 7.5);

    focus.append("text")
        .attr("x", 15)
        .attr("dy", ".31em");

    svg.append("rect")
        .attr("transform", "translate(" + margin.left + "," + margin.top + ")")
        .attr("class", "overlay")
        .attr("width", width)
        .attr("height", height)
        .on("mouseover", function() { focus.style("display", null); })
        .on("mouseout", function() { focus.style("display", "none"); })
        .on("mousemove", () => {
          var x0 = x.invert(d3.mouse(this)[0]),
              i = bisectDate(data, x0, 1),
              d0 = data[i - 1],
              d1 = data[i],
              d = x0 - d0.year > d1.year - x0 ? d1 : d0;
          focus.attr("transform", "translate(" + x(d.year) + "," + y(d.value) + ")");
          focus.select("text").text(function() { return d.value; });
          focus.select(".x-hover-line").attr("y2", height - y(d.value));
          focus.select(".y-hover-line").attr("x2", width + width);
        });
  }

  render() {
    const { width, height } = this.props
    return  (
      <svg innerRef={ this.wrapper } height={ height } width={ width } className="mySvg"></svg>
    )
  }
}

我在父组件中渲染 LineChart 组件，如下所示：

  <LineChart
    width={ 1000 }
    height={ 350 }
    margin={ 50 }
    data={[
      { year: 2011, value: 3 },
      { year: 2012, value: 20 },
      { year: 2013, value: 2 },
      { year: 2014, value: 12 },
      { year: 2015, value: 8 },
      { year: 2016, value: 14 },
      { year: 2017, value: 8 }
    ]}
  />

错误：

Answer 1

问题出在线路上.on("mousemove", () => {})。您正在使用一个粗箭头函数，它没有自己的函数this，而是有效地使用上部作用域 this 。当使用“经典”函数定义时（就像对“mouseover”所做的那样），这会保留this（作为“mousemove”目标的节点）的正确值。

svg.append("rect")
    ...
    .on("mousemove", function () {
     // this is the node which was target of "mouseover" event
    })

我设置了一个演示。