Check out example codes for "jqury get selected option". It will help you in understanding the concepts better.
Code Example 1
<select id="myselect">
<option value="1">Mr</option>
<option value="2">Mrs</option>
<option value="3">Ms</option>
<option value="4">Dr</option>
<option value="5">Prof</option>
</select>
<script>
$( "#myselect option:selected" ).val();
</script>
Learn ReactJs, React Native from akashmittal.com