Get CDN asset URL

helpers.php

<?php

if (! function_exists('asset_path')) {
    /**
     * Get the path to a versioned Mix file.
     *
     * @param  string  $path
     * @param  string  $manifestDirectory
     * @return \Illuminate\Support\HtmlString|string
     *
     * @throws \Exception
     */
    function asset_path($path, $manifestDirectory = '')
    {
        $mixPath = mix($path, $manifestDirectory);
        $cdnUrl  = config('assets.cdn_url');
        $env     = config('app.env');

        // Reference CDN assets only in production or staging environemnt.
        // In other environments, we should reference locally built assets.
        if ($cdnUrl && ($env === 'production' || $env === 'staging')) {
            $mixPath = $cdnUrl . $mixPath;
        }

        return $mixPath;
    }
}

this file goes on app/helpers/helpers.php?