Adding javascript blocks to a single file and adding it to the header

Just chuck them in a file, say your-theme/js/global.js and enqueue it in functions.php:

function wpse_180397_scripts() {
    wp_enqueue_script(
        'wpse-180397-global', /* Unique ID */
        get_bloginfo( 'template_url' ) . '/js/global.js', /* URL */
        array(), /* Dependencies */
        true /* In footer */
    );
}

add_action( 'wp_enqueue_scripts', 'wpse_180397_scripts' );