javascript-onclick-onsubmit
<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 onclick="document.getElementById('field2').value=
document.getElementById('field1').value">Copy Text</button>
</body>
</html>
<FORM ACTION="javascript-form-validation.htm" NAME="testform" onSubmit="return validateMyForm()">
</form>
<script type="text/javascript" language="javascript">
function validateMyForm()
{
var tempvalue = document.getElementById( 'userinput' ).value;
alert( tempvalue );
}
</script>