where to host my react fornt end and express endpoint that interact with smart contract to be fully decentralised. Are there any option to host it decentralised any cloud provider other than traditional centralised options like aws,gcp,azure. IPFS and Storj are file storage i want to run my reactjs fornt end app.
I'm not sure to correctly understand your question. If you want to create a fully decentralized application I advise you to read the Ethereum book, chapter 12 : https://github.com/ethereumbook/ethereumbook/blob/develop/12dapps.asciidoc .
Swarm is a good alternative to IPFS to host the frontend in a decentralized way : https://ethersphere.github.io/swarm-home/ .
According to the Ethereum book :
Swarm is another content-addressable P2P storage system, similar to IPFS. Swarm was created by the Ethereum Foundation, as part of the Go-Ethereum suite of tools. Like IPFS, it allows you to store files that get disseminated and replicated by Swarm nodes. You can access any Swarm file by referring to it by a hash. Swarm allows you to access a website from a decentralized P2P system, instead of a central web server.