<html>
<body>
<button οnclick="document.getElementById('field2').value=
document.getElementById('field1').value">Copy Text</button>
</body>
</html>
<html>
<body>
Field1: <input type="text" id="field1" value="Hello World!">
<br />
Field2: <input type="text" id="field2">
<br /><br />
Click the button below to copy the content of Field1 to Field2.
<br />
<button οnclick="document.getElementById('field2').value=
document.getElementById('field1').value">Copy Text</button>
</body>
</html>