Adding a vertical line to a D3v7 chart, that follows the mouse pointer.

d3v7-mouse-over-line.ts

const vertical = d3.select(".chart")
        .append("div")
        .attr("class", "remove")
        .style("position", "absolute")
        .style("z-index", "19")
        .style("width", "1px")
        .style("height", "100%")
        .style("top", "0px")
        .style("left", "0px")
        .style("background", "#000000");

d3.select(".chart")
  // @ts-ignore
  .on("mousemove", function (event: MouseEvent, _d, _i) {
      vertical.style("left", `${event.pageX}px` )
  })
  // @ts-ignore
  .on("mouseover", function (event: MouseEvent, _d, _i) {
          vertical.style("left", `${event.pageX}px`)
  });