how to upload files to s3 without using Access key from EC2 through React Js

Hello.

If the execution environment is EC2, you can access S3 using an IAM role.
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-roles-for-amazon-ec2.html#working-with-iam-roles

Hi. We can also use IMDS v2 on EC2 to get credential.
https://docs.aws.amazon.com/ko_kr/AWSEC2/latest/UserGuide/configuring-instance-metadata-service.html

<Example commend>.

1. to get token.
   TOKEN= 'curl -X PUT "http://169.254.169.254/latest/api/token" -H "X-aws-ec2-metadata-token-ttl-seconds:21600"'

2. to get credential from IAM role.
   curl -H "X-aws-ec2-metadata-token:$TOKEN" -v http://169.254.169.254/latest/meta-data/iam/security-credentials/<IAM-role>

But IMDS2 looks like it does not support recat js.
https://docs.aws.amazon.com/ko_kr/AWSEC2/latest/UserGuide/use-a-supported-sdk-version-for-imdsv2.html