How to determine if object exists AWS S3 Node.JS sdk

by using headObject method

AWS.config.update({
        accessKeyId: "*****",
        secretAccessKey: "****",
        region: region,
        version: "****"
    });
const s3 = new AWS.S3();

const params = {
        Bucket: s3BucketName,
        Key: "filename" //if any sub folder-> path/of/the/folder.ext
}
try {
        await s3.headObject(params).promise()
        console.log("File Found in S3")
    } catch (err) {
        console.log("File not Found ERROR : " + err.code)
}

As params are constant, the best way to use it with const. If the file is not found in the s3 it throws the error NotFound : null.

If you want to apply any operations in the bucket, you have to change the permissions of CORS Configuration in the respective bucket in the AWS. For changing permissions Bucket->permission->CORS Configuration and Add this code.

<CORSConfiguration>
<CORSRule>
    <AllowedOrigin>*</AllowedOrigin>
    <AllowedMethod>PUT</AllowedMethod>
    <AllowedMethod>POST</AllowedMethod>
    <AllowedMethod>DELETE</AllowedMethod>
    <AllowedMethod>GET</AllowedMethod>
    <AllowedMethod>HEAD</AllowedMethod>
    <AllowedHeader>*</AllowedHeader>
</CORSRule>
</CORSConfiguration>

for more information about CORS Configuration : https://docs.aws.amazon.com/AmazonS3/latest/dev/cors.html

The simplest solution without try/catch block.

const exists = await s3
  .headObject({
    Bucket: S3_BUCKET_NAME,
    Key: s3Key,
  })
  .promise()
  .then(
    () => true,
    err => {
      if (err.code === 'NotFound') {
        return false;
      }
      throw err;
    }
  );

Before creating the signed URL, you need to check if the file exists directly from the bucket. One way to do that is by requesting the HEAD metadata.

// Using callbacks
s3.headObject(params, function (err, metadata) {  
  if (err && err.name === 'NotFound') {  
    // Handle no object on cloud here  
  } else if (err) {
    // Handle other errors here....
  } else {  
    s3.getSignedUrl('getObject', params, callback);  
    // Do stuff with signedUrl
  }
});

// Using async/await
try {
  await s3.headObject(params).promise();
  const signedUrl = s3.getSignedUrl('getObject', params);
  // Do stuff with signedUrl
} catch (error) {
  if (error.name === 'NotFound') { // Note with v3 AWS-SDK use error.code
    // Handle no object on cloud here...
  } else {
    // Handle other errors here....
  }
}