simple text animation counter

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v2.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  </style>
</head>

<body>
  <script>
    // Feel free to change or delete any of the code you see in this editor!
    var svg = d3.select("body").append("svg")
      .attr("width", 960)
      .attr("height", 500)

svg.append("text")
      .text("Edit the code below to change me!")
      .attr("y", 200)
      .attr("x", 120)
      .attr("font-size", 36)
      .attr("font-family", "monospace")
let end_val = [25, 100];
    
    svg.selectAll(".txt")
    .data(end_val)
    .enter()
    .append("text")
    .text(0)
    .attr("class", "txt")
    .attr("x", 10)
    .attr("y", function(d, i) {
        return 50 + i * 30
    })
    .transition()
    .duration(3000)
    .tween("textTween", function(d) {
        var i = d3.interpolate(this.textContent, d);
        return function(t) {
//           console.log(t)
          // t is the percent completion of the transition
          this.textContent = Math.round(i(t));
        }
      });
    // alternate
//       .tween("text", function(d) {
//       var i = d3.interpolate(0, d);
//       return function(t) {
//         d3.select(this).text(Math.round(i(t)));
//       };
//     });
  </script>
</body>

https://d3js.org/d3.v2.min.js