text: class Tooltip {
    constructor(extraClass) {
      this.div = d3
        .select("body")
        .append("div")
        .attr("class", "tooltip")
        .style("opacity", 0);
  
      if(extraClass)
        this.div.classed(extraClass,true)
  
    }
  
    show(html, left, top){
      let opacity = this.div.classed("storyTooltip") ? 1 : .9
      this.div.transition()
        .duration(200)
        .style("opacity", opacity);
      this.div.html(html)
        .style("left", (left ? left : (d3.event.pageX + 28)) + "px")
        .style("top", (top ? top : (d3.event.pageY - 28)) + "px");
    }
  
    hide(){
      this.div.transition()
        .duration(500)
        .style("opacity", 0);
    }
  
    setFont(font){
      this.div.style("font",font)
    }
  }
  