JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.7.1/Chart.bundle.min.js"></script>
<p>
<b style="color: red">red</b> is shadow
</p>
<canvas id="canvas" width="200" height="100"></canvas>

Babel + JSX

const ShadowLineElement = Chart.elements.Line.extend({
  draw () {
    

		console.log(this)

    const { ctx } = this._chart

    const originalStroke = ctx.stroke

    ctx.stroke = function () {
      ctx.save()
      ctx.shadowColor = 'red'
      ctx.shadowBlur = 0
      ctx.shadowOffsetX = 0
      ctx.shadowOffsetY = 8
      originalStroke.apply(this, arguments)
      ctx.restore()
    }
    
    Chart.elements.Line.prototype.draw.apply(this, arguments)
    
    ctx.stroke = originalStroke;
  }
})

Chart.defaults.ShadowLine = Chart.defaults.line
Chart.controllers.ShadowLine = Chart.controllers.line.extend({
  datasetElementType: ShadowLineElement
})

new Chart(document.getElementById('canvas'), {
      type: 'ShadowLine',
      data: {
        datasets: [
          {
          	label: 'somedata',
            fill: false,
            borderColor: 'green',
          	data: [
            	10, 20
            ]
          }
        ]
      }
    })