JSFiddle - React, Tailwind, and code Playground

JavaScript

var svg = d3.select("body")
        .append("svg")
        .attr("width", 500)
        .attr("height", 500);

// code, code, code, irrelevant code...
function timeForTimeline() { // har
    var timeline = svg.append("line")
        .attr("stroke", "steelblue");
    repeat();
    
    function repeat() {
      timeline
        .attr('x1', 0)
        .attr('y1', 130)
        .attr('x2', 168)
        .attr('y2', 130)
		.transition()
      .duration(4000)
      .ease(d3.easeLinear)
        .attr('x1', 0)
        .attr('y1', 430)
        .attr('x2', 168)
        .attr('y2', 430)
      .on("end", repeat);
   }
}



timeForTimeline();