如何从<a data-=""> to clipboard

Question

As you can see from the snippet, the "Copy to Clipboard" function works when the text comes from <input value="text">, but I am failing to replicate the same function when the text comes from <a data-text="text">.

I'm assuming copyText.select() is limited to value from input and textarea only.

What would be the easiest way to make copy text from <a> work?

function copyFromButton(id) {
  alert("Clicked but not copied:" + document.getElementById(id).dataset.text);
  /* Get the text field */
  var copyText = document.getElementById(id).dataset.text;
  /* Select the text field */
  copyText.select();
  /* Copy the text inside the text field */
  document.execCommand("copy");
  /* Alert the copied text */
  alert("Copied the text: " + copyText.value);
}

function copyFromInput(id) {
  /* Get the text field */
  var copyText = document.getElementById(id);
  /* Select the text field */
  copyText.select();
  /* Copy the text inside the text field */
  document.execCommand("copy");
  /* Alert the copied text */
  alert("Copied the text: " + copyText.value);
}

<a class="btn" id="buttonCopy" data-text="text to be copied from button" onClick="copyFromButton(this.id)"> Cick to Copy </a>
<hr>
<input type="text" onclick="copyFromInput(this.id)" id="myInputRec" value="text to be copied from input" readonly="readonly" >