<input type="button"
	id="btn"
	value="実行"
	onclick='alert("OK");'>

<input type="button"
	id="btn"
	value="実行"
	onclick='location.href="<?= $_SERVER['SCRIPT_NAME'] ?>";'>

<input type="button"
	id="btn"
	value="実行"
	onclick='location.reload(true);'>

document.getElementById("id").value
document.frmName.fldName.value
document.getElementsByName("name")[0].value
document.getElementsByTagName("tagName")[0]

(new Date()).getTime()