Get elements then inject opacity from 0 to 1

my-opacity.js

document.addEventListener('DOMContentLoaded', () => {
  var myOpacity = 0;
  var readMeter = document.getElementsByClassName('bsf-rt-display-label')[0];
  var readUnit = document.getElementsByClassName('bsf-rt-display-postfix')[0];
  var readColor = document.getElementsByClassName('bsf-rt-reading-time')[0];

  function MyFadeFunction() {
    if (myOpacity < 1) {
      myOpacity += 0.075;
      setTimeout(function () {
        MyFadeFunction();
      }, 1000);
    }
    document.getElementById('means__read__meter').style.opacity = myOpacity;

    readMeter.setAttribute('prefix', 'ใช้เวลาอ่าน');
    readUnit.setAttribute('postfix', 'นาที');
    readColor.setAttribute('style', 'color: #0984e3;');
  }

  MyFadeFunction();
});