User selects city from options in form and pass longitude and latitude to api

Question

I want to pass longitude and latitude to the geonames api. Currently I have two select fields where a user selects the city longitude and the corresponding city latitude:

<select id="selectLat">
    <option value="30.26057">Chicago Latitude</option>
    <option value="51.5074">London Latitude</option>
    <option value="50.0755">Prague Latitude</option>
    
</select>

<select id="selectLng">
    <option value="-97.771889">Chicago Longitude</option>
    <option value="0.1278">London Longitude</option>
    <option value="14.4378">Prague Longitude</option>
</select>
            

Once selections are submitted the values are passed to the geonames api and I'm able use the JSON data returned. But what I actually want to happened is that a user simply selects the city name only. The longitude and latitude values would be combined and are then somehow parsed/separated and passed to the api. Are there ways to do this?

I'm using jQuery and php to handle the api request btw.

$.ajax({
            url: "test.php",
            type: 'POST',
            dataType: 'json',
            data: {
                 lat: $('#selectLat').val(),
                 lng: $('#selectLng').val()
            },

Answer 1

You could use data- attributes, eg:

<option data-longitude="..." data-latitude="...">city</option>

then

    $.ajax({
        url: "test.php",
        type: 'POST',
        dataType: 'json',
        data: {
             lat: $('#citySelect option:selected').data("latitude"),
             lng: $('#citySelect option:selected').data("longitude"),
        },

Answer 2

Maintain an array so that you have for each city its longitude and latitude, When selecting a city you will remove the information from the array from the array.

HTML:

 <select id="select_city">
                <option value="chicago">Chicago Latitude</option>
                <option value="london">London Latitude</option>
                <option value="prague">Prague Latitude</option>
                
        </select>

JS:

 const c = "{'prague' : {'latitude': 50.0755, 'longitude': 14.4378}, 'london': {'latitude': 50.0755, 'longitude':14.4378}}";
 .
 .
 .
 lat = c[${'#select_city').val()].latitude;
 lng = c[${'#select_city').val()].longitude;

  $.ajax({
            url: "test.php",
            type: 'POST',
            dataType: 'json',
            data: {
                 lat: lat,
                 lng: lng
            },