mastersss,
<input id="field_54ef5f88727d7_200_field_54ef5f88727da">
<input id="field_54ef5f88727d7_2_field_54ef5f88727da">
<input id="field_54ef5f88727d7_7_field_54ef5f88727da" value="test">
<script>
alert(document.querySelector('[id$="54ef5f88727da"]:last-of-type').value);
</script>