Cómo seleccionar texto por un botón en HTML

<html>
<br><br>
<input type="text" value="Enter your text here!
" id="myInput">
<script>
function myFunction() {
  /* Get the text field */
  var copyText = document.getElementById("myInput");

  /* Select the text field */
  copyText.select();
  copyText.setSelectionRange(0, 99999); /* For mobile devices */

   /* Copy the text inside the text field */
  navigator.clipboard.writeText(copyText.value);

  /* Alert the copied text */
  alert("Copied the text: " + copyText.value);
}
</script>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
.tooltip {
  position: relative;
  display: inline-block;
}

.tooltip .tooltiptext {
  visibility: hidden;
  width: 140px;
  background-color: #555;
  color: #fff;
  text-align: center;
  border-radius: 6px;
  padding: 5px;
  position: absolute;
  z-index: 1;
  bottom: 150%;
  left: 50%;
  margin-left: -75px;
  opacity: 0;
  transition: opacity 0.3s;
}

.tooltip .tooltiptext::after {
  content: "";
  position: absolute;
  top: 100%;
  left: 50%;
  margin-left: -5px;
  border-width: 5px;
  border-style: solid;
  border-color: #555 transparent transparent transparent;
}

.tooltip:hover .tooltiptext {
  visibility: visible;
  opacity: 1;
}
</style>
</head>
<body>
<div class="tooltip">
<button onclick="myFunction()" onmouseout="outFunc()">
  <span class="tooltiptext" id="myTooltip">Select the entire text</span>
  Select text
  </button>
</div>

<script>
function myFunction() {
  var copyText = document.getElementById("myInput");
  copyText.select();
  copyText.setSelectionRange(0, 99999);
  navigator.clipboard.writeText(copyText.value);
  
  var tooltip = document.getElementById("myTooltip");
  tooltip.innerHTML = "Selected!";
}

function outFunc() {
  var tooltip = document.getElementById("myTooltip");
  tooltip.innerHTML = "Select the entire text";
}
</script>
</html>
Gabriel Galvez