Ah I just had this problem myself! And while _embed is great, in my experience it is very slow, and the point of JSON is to be fast 😀
I have the following code in a plugin (used for adding custom post types), but I imagine you could put it in your theme’s function.php file.
php
add_action( 'rest_api_init', 'add_thumbnail_to_JSON' );
function add_thumbnail_to_JSON() {
//Add featured image
register_rest_field(
'post', // Where to add the field (Here, blog posts. Could be an array)
'featured_image_src', // Name of new field (You can call this anything)
array(
'get_callback' => 'get_image_src',
'update_callback' => null,
'schema' => null,
)
);
}
function get_image_src( $object, $field_name, $request ) {
$feat_img_array = wp_get_attachment_image_src(
$object['featured_media'], // Image attachment ID
'thumbnail', // Size. Ex. "thumbnail", "large", "full", etc..
true // Whether the image should be treated as an icon.
);
return $feat_img_array[0];
}
Now in your JSON response you should see a new field called "featured_image_src": containing a url to the thumbnail.
Read more about modifying responses here:
http://v2.wp-api.org/extending/modifying/
And here’s more information on theregister_rest_field and wp_get_attachment_image_src() functions:
1.) https://developer.wordpress.org/reference/functions/register_rest_field/
2.) https://developer.wordpress.org/reference/functions/wp_get_attachment_image_src/
**Note: Don’t forget <?php ?> tags if this is a new php file!