Web3.js – Building a Custom Web3 Provider

web3-providersweb3js

I wonder if there are any tutorials / guides out there that explain how to create your own web3 provider (like metamask), what to consider when creating one, how to handle security/privacy issues, what are the best practices and such..

I know for example that web3 provider, should implement the web3.js library, and to export some of its functions for external use. and if for example I want to create a chrome extension, my provider should inject the web3 object into the host window.

I know that my question is too general, but I am looking for some guidance basically, just to give me a lead to start.

Just to be clear, I am looking for a way to build a chrome extension that will be the web3 provider, in other words I want to build my own Metamsk / parity extension

Best Answer

You are asking about very niche and complex problem, so one cannot expect ready made tutorials to be available.

I would suggest

Reverse engineering web3.js
Reverse engineering MetaMask
Reverse engineering Trust wallet
Reverse engineering web3.py (might be the most readable source code of all these)

Related Solutions

[Ethereum] Web3 not being detected – google chrome extension

This code checks for check for instance already available in window

var web3 = window.web3

If found, check for Mist/Metamask or any other provider, and return web3, and console outputs to 'Injected web3 detected.'

// Use Mist/MetaMask's provider.
  web3 = new Web3(web3.currentProvider)

  results = {
    web3: web3
  }

  console.log('Injected web3 detected.');

else if web3 instance is not found, this code fallback to localhost node web3 provider, so console outputs to 'No web3 instance injected, using Local web3.'

// Fallback to localhost if no web3 injection. We've configured this to
  // use the development console's port by default.
  var provider = new Web3.providers.HttpProvider('http://127.0.0.1:9545')

  web3 = new Web3(provider)

  results = {
    web3: web3
  }

  console.log('No web3 instance injected, using Local web3.');

As in your case you are not running local ethereum node, it is throwing error.

But as suggested by me, you have replaced localhost link with infura link.

Now there is no error.Why? because web3 has been injected.

But still console output is same, it's because console command still is same.

 console.log('No web3 instance injected, using Local web3.');

To check whether web3 has been instantiated & injected, just check web3 version

console.log(web3.version.api) // for web3 0.2x.x

console.log(web3.version) // for web3 1.0

Web3.js Metamask – Where is Metamask’s Provider?

Metamask uses Infura as you can see here:

https://github.com/MetaMask/metamask-extension/blob/5f3f8c85fcc5bd378ef1a886434a3e98546fee7f/app/scripts/controllers/network/enums.js

EDIT: It seems they have made some changes and now they are using this package: https://github.com/kumavis/eth-json-rpc-infura

Best Answer

Related Solutions

[Ethereum] Web3 not being detected – google chrome extension

Web3.js Metamask – Where is Metamask’s Provider?

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