by default selected dropdown jquery code example
Example 1: select dropdown default value
<select>
<option value="" selected disabled hidden>Choose here</option>
<option value="1">One</option>
<option value="2">Two</option>
<option value="3">Three</option>
<option value="4">Four</option>
<option value="5">Five</option>
</select>
Example 2: To set the dropdown default value using jquery
$("#SelectPayment option:selected").val('Cash');