JSFiddle - React, Tailwind, and code Playground

HTML

<form name="frm" id="frm" action="http://excavator.net.au/test1.php" method="post" enctype="multipart/form-data">
<table>
	<tr>
            	<td>Address :</td>
                <td><input type="text" name="address"  value="" /></td>
            </tr>

            <tr>
            	<td>Suburb :</td>
                <td id="suburb_cnt"><input name="suburb1" type="text" value="Newtown" /></td>
            </tr>
			
			<tr>
            	<td>Postcode :</td>
                <td><input type="text" name="zip" id="zip"  value="" /></td>
            </tr>
			
			<tr>
            	<td>State :</td>
                <td id="state_cnt"><input type="text" name="state" id="state"  value="" /></td>
            </tr>
			<tr>
            	<td></td>
                <td><input type="submit" value="submit" name="submit" /></td>
            </tr>			
</table>
</form>

JavaScript

$("#zip").on('blur',function(){
    var sel = '<select id="suburb" name="suburb1"><option value="ALEXANDRIA">ALEXANDRIA, New South Wales</option><option value="BEACONSFIELD">BEACONSFIELD, New South Wales</option><option value="EVELEIGH">EVELEIGH, New South Wales</option></select>';
    $("#suburb_cnt").html(sel);
});