JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://canvasjs.com/assets/script/canvasjs.min.js"></script>
<br/><!-- Just so that JSFiddle's Result label doesn't overlap the Chart -->
<div id="chartContainer" style="height: 360px; width: 100%;"></div>

JavaScript

var chart = new CanvasJS.Chart("chartContainer", {
  axisY: {
    stripLines: [{
      startValue: 50,
      endValue: 70
    },{
      //value: 45,
      label: "Stripline Label",
      color: "transparent",
      labelFontColor:"black"
    }]
  },
  data: [{
    type: "line",
    dataPoints: [
      { x: 10, y: 71 },
      { x: 20, y: 55 },
      { x: 30, y: 50 },
      { x: 40, y: 65 },
      { x: 50, y: 155 },
      { x: 60, y: 68 },
      { x: 70, y: 28 },
      { x: 80, y: 34 },
      { x: 90, y: 14 }
    ]
  }]
});

chart.render();

var refStripline = chart.axisY[0].stripLines[0], currStripline = chart.axisY[0].stripLines[1];
updateStripLineValue(currStripline, refStripline)

function updateStripLineValue(currStripline, refStripline) {
  var padding = 2; //In pixels
  var font = currStripline.labelFontWeight + " " + currStripline.labelFontSize + "px " + currStripline.labelFontFamily;
  var labelHeight = getHeight(currStripline.label, font);
  currStripline.set("value", currStripline.parent.convertPixelToValue(currStripline.parent.convertValueToPixel(Math.min(refStripline.startValue,refStripline.endValue)) + labelHeight + padding));

}

function getHeight(txt, font){
  var tempCanvas = document.createElement("canvas");
  var tempCtx = tempCanvas.getContext("2d");

  tempCtx.font = font;	
  return parseInt(tempCtx.font.match(/\d+/), 10);
}