upload to s3 with fileS buffer - node.js

Question

I am trying to upload to s3 with bulk files.
Somehow if I am uploading with callback, it'll work properly but I want to push all the return data into an array then do something after. But it doesn't work.
I looked online, I was saw answers such as using async await or recurssive would work but still it's not working though. I even tried using reduce but no luck too
example of my reduce
return files.reduce((accumulator, current) => {
const {path, buffer} = current;
const s3 = new AWS.S3();
// https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#putObject-property
s3.putObject(awsS3sdkParams(path, buffer), function ( err, data ) {
const { protocol, host } = this.request.httpRequest.endpoint;
data.params = this.request.params;
data.params.url = `${protocol}//${host}/${data.params.Key}`;
return [...accumulator, data];
});
}, []);
example using recurrsive
const result = [];
const helper = (files) => {
const {path, buffer} = files[0];
const s3 = new AWS.S3();
// https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#putObject-property
s3.putObject(UploadService.awsS3sdkParams(path, buffer), function (err, data){
const { protocol, host } = this.request.httpRequest.endpoint;
data.params = this.request.params;
data.params.url = `${protocol}//${host}/${data.params.Key}`;
UtilsService.clDebug(data, 'data');
result.push(data);
files.shift();
if(files.length > 0) return helper(files);
});
};
helper(files);
return results;
example using promise
const result = [];
for(let {path, buffer} of files){
const s3 = new AWS.S3();
s3.putObject(awsS3sdkParams(path, buffer)).promise()
.then(file => {
result.push(file);
})
.catch(err => {
console.log(err, 'errs');
});
}
I can pretty much understand why result is always [] but how can I make it work though?
Reason why I cannot use async await is because I tried but then somehow after files are either uploaded with bad data that I cannot even open the file, or keys would be the same...
Does anyone has any other suggestions or advice?
Thanks in advance for any