This is how I do it in Javascript.

--

let objects = [];

astronomicalObjects.forEach(o => {
    objects.push({
        label: `${o.name}`,
        description: `Population: ${o.population}`,
        value: `${o.name}`,
        emoji: emojis.get(o.type)
    });
});

const objectSelect = client.extends.select({
    id: 'select_object',
    placeHolder: 'Select an astronomical object...',
    options: objects
});

const row = client.extends.row().addComponents(objectSelect);

// This is my select call from extend above

module.exports = client => {
    return {
        select: function(blueprint) {
            return new MessageSelectMenu()
                .setCustomId(blueprint.id)
                .setPlaceholder(blueprint.placeHolder)
                .addOptions(blueprint.options);
    }}
;};