This should work.
$(".formData").val("valuesgoeshere")
For empty
$(".formData").val("")
If this does not work, you should post a jsFiddle.
Demo:
$(function() {_x000D_
$(".resetInput").on("click", function() {_x000D_
$(".formData").val("");_x000D_
});_x000D_
})
_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>_x000D_
<input type="text" class="formData" value="yoyoyo">_x000D_
_x000D_
_x000D_
<button class="resetInput">Click Here to reset</button>
_x000D_