【AWS】wwwなしからwwwありのURLにリダイレクトさせる

function handler(event) {
    var request = event.request;
    var host = request.headers.host.value;
    var uri = request.uri;

    if (!host.includes('cloudfront.net') && !host.startsWith('www')) {
        return {
            statusCode: 301,
            statusDescription: 'Moved Permanently',
            headers: { location: { value: 'https://www.' + host + uri } }
        };
    }

    return request;
}