I was exploring Hyperledger fabric's fabric-samples repository. I am confused between these two files - application-gateway-go and application-javascript (apart from both are in different language). Both these files make connection, query and update the ledger. What is the purpose of these two ?
When and where to use them ? Why they didn't wrote gateway file is javascript ?
For each of the Fabric chaincode samples, corresponding client application samples are provided in the application-* directories. These client application samples are provided by community volunteers and therefore you'll see various language samples contributed based on the goodwill of community members.
Additionally, as of Fabric v2.4 there are new Gateway SDKs in each of the languages that utilize the simplified Gateway programming model in Fabric v2.4 and above. The Gateway SDKs are strategic and you will generally see the Gateway SDK application samples replace the legacy SDK application samples over time.
More information about the fabric samples can be found in the readme.
More information about the new Gateway SDKs can be found in the Gateway documentation.