Exporting Docx File with content disposition using AWS Lambda function - node.js

Question

I am writing a handler as AWS Lambda Function which is supposed to wrap the content into the docx file. I am using the Content-Disposition in response headers in order to achieve the objective. Below is the code that I have written so far:
//Process Array Buffer and extract the plain content out of it
export const extractContent = async (data: Buffer) => {
return new Promise((resolve, reject) =>
textract.fromBufferWithMime(
"application/vnd.openxmlformats-officedocument.wordprocessingml.document",
data,
{ preserveLineBreaks: true },
(err, content) => {
if (err) {
reject(err);
} else {
resolve(content);
}
}
)
);
};
export const handlerName = async (
event: APIGatewayProxyEvent
): Promise<APIGatewayProxyResult> => {
if (event.body === null) {
return ErrorResponse;
}
const result = await class.func(JSON.parse(event.body)); //returns an array buffer object
if (result instanceof Error) {
return ErrorResponse;
}
const content = await extractContent(result.data)
.then(res => res)
.catch(err => err);
const headers = {
"Access-Control-Allow-Origin": "*",
"Strict-Transport-Security": "'max-age=31536000'",
"Access-Control-Expose-Headers": "Content-Disposition",
"Content-Disposition": attachment; filename=fn.docx; filename*=UTF-8''fn.docx,
"Content-Type": "application/vnd.ms-word.document"
};
return {
body: content,
headers,
statusCode: 200,
};
};
Now only string can be returned in APIGatewayResponse; hence I am not able to return byte object | stream | buffer instead.
I am able to download the docx file but it is not getting opened in MS-Word; I am always getting a detailed error that either file is corrupt or some part is invalid or missing.
I have already tried the base64 encoded string but still not able to get what is desired. Please suggest a solution to it.
I writing the handler in typescript Node using the SLS framework.