copy.js

copy.js

<style>
.blind {
    overflow: hidden;
    position: absolute;
    clip: rect(0 0 0 0);
    width: 1px;
    height: 1px;
    margin: -1px;
}
</style>

<textarea id="copy" class="blind" readonly>
your copy text here!
</textarea>

<script>
copyClipboard(document.getElementById('copy'));

function copyClipboard(el) {
  el.select();
  window.document.execCommand('copy');
}
</script>