localize_script but data changes dependent on product ID

You should call wp_localize_script() in the wp_enqueue_scripts hook (or a later hook) in which you would get the correct product/post data such as ID, and that conditional tags like is_single() would also work as expected.

So you should move all the $product, $product_id, $dataToBePassed and wp_localize_script() parts to inside the wp_enqueue_scripts callback, and then you’d get the correct product/post ID, etc. See an example below, and note that:

• is_product() and wc_get_product() are WooCommerce functions, and I used the former because I presumed your script should only be loaded on single product pages? (like one at example.com/product/product-foo/)

• Also, just like one should do $post = get_post(), you should also do $product = wc_get_product() to properly get the current product/post object/data.

add_action( 'wp_enqueue_scripts', 'my_theme_enqueue_three_d_scripts' );
function my_theme_enqueue_three_d_scripts() {
    if ( ! is_product() ) {
        return;
    }

    $handle="three-d-scripts";
    $src     = get_stylesheet_directory_uri() . '/src/scripts/three-d-scripts.js';
    $deps    = array();
    $version = '1.0.0';
    wp_enqueue_script( $handle, $src, $deps, $version, true );

    $product        = wc_get_product();
    $product_id     = $product ? $product->get_id() : 0;
    $dataToBePassed = array();

    switch ( $product_id ) {
        case 1:
            $dataToBePassed = array( 'product_id' => 1 );
            break;

        case 2:
            $dataToBePassed = array( 'product_id' => 2 );
            break;

        default:
            $dataToBePassed = array( 'product_id' => 0 );
            break;
    }

    // PS: Instead of php_vars, use a unique name like my_three_d_vars..
    wp_localize_script( $handle, 'php_vars', $dataToBePassed );
}