<button id="myId" onclick="heyThere()">Click!</button>

<script>
  function heyThere() {
    alert(myId.innerHTML);
  }
</script>
body {
  display: grid;
  place-items: center;
  height: 100vh;
}

button {
  background: #ff7a18;
  border: none;
  color: #fff;
  padding: 1rem 1.5rem;
}

External CSS

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External JavaScript

This Pen doesn't use any external JavaScript resources.