wordpress ulike rest api add-on -- https://wordpress.org/plugins/wp-ulike/

functions.php

<?php
//ulike add post
add_action('rest_api_init', 'stnc_register_ulike');
function stnc_register_ulike() {
    register_rest_field('post', '_liked', array('get_callback' => 'stnc_get_ulike', 'update_callback' => 'stnc_update_ulike', 'schema' => null,));
}
/**
 * Handler for getting custom field data.
 */
function stnc_get_ulike($object, $field_name, $request) {
    return get_post_meta($object['id'], $field_name);
}
/**
 * Handler for updating custom field data.
 */
function stnc_update_ulike($value, $object, $field_name) {
    if (!$value || !is_string($value)) {
        return;
    }
    return update_post_meta($object->ID, $field_name, strip_tags($value));
}