<form id="form1" action="" method="post" runat="server">
<input name="inp" id="inp" value="1" />
</form>

document.getElementById("form1").reset();

document.formName.reset();

$("#inp").val("1");

$("input").val("");

<form id="form1" action="" method="post" runat="server">
<input name="inp" id="inp" value="1" />
<input id="res" name="res" type="reset" style="display:none;" />
</form>

$("input[name='res']").click();