JavaScript read more/less (+/-) button not working in IE

Question

the following 'read more' text expand '+/-' button script is functioning in Chrome but not IE. I can see some threads saying let should now work in IE11. Can anyone help me correct this script to function in both browsers?

Thanks in advance!

    <table>
  <tr>

          <td class="definition" data-keyword="dog"> 
              <button onclick="expandMore('dog')" class="myBtn">+</button><strong>Definition of a dog</strong> a domesticated carnivorous mammal that typically has         
              <span class="threeDots"> ... </span>
              <span class="hiddenText" style="display: none;"><br>a long snout, an acute sense of smell, non-retractable claws, and a barking, howling, or whining voice.</span>              
          </td>
        <td>8 (3)(d)</td>
      </tr>

</table>

<script>
function expandMore(keyword) {
    let threeDots = document.querySelector(`.definition[data-keyword="${keyword}"] .threeDots`);
    let hiddenText = document.querySelector(`.definition[data-keyword="${keyword}"] .hiddenText`); 
    let btnText = document.querySelector(`.definition[data-keyword="${keyword}"] .myBtn`);

    if (threeDots.style.display === "none") {
        threeDots.style.display = "inline";
        btnText.textContent = "+";
        hiddenText.style.display = "none";
    } else {
        threeDots.style.display = "none";
        btnText.textContent = "-"; 
        hiddenText.style.display = "inline";
    }
}
</script>

Answer 1

I think template literal is not yet supported by IE. If you look at the: https://kangax.github.io/compat-table/es6/

Change it to

let threeDots = document.querySelector('.definition[data-keyword="' + keyword + '"] .threeDots');

Or transpile it using Babel https://babeljs.io/