avoid race conditions with web3 and be ready for new ethereum provider system ( provider.enable() ) 2nd. nov 2018

web3_resolver_ethereum_provider_2018.js

/* global window */

// originally from: https://github.com/adrianmcli
// adapted by me

import Web3 from 'web3'


const fallback = 'wss://mainnet.infura.io/ws'


function resolveWeb3(resolve, reject){
  
  // Modern dapp browsers...
  if (window.ethereum) {
      console.log('web3, using ethereum provider')
      
      window.web3 = new Web3(window.ethereum);

      window.ethereum
        .enable()
        .then( _ => {
          resolve(window.web3)
        })
        .catch( err => { 
          console.warn('access denied by user', err)
          reject()
        })
        
  }
  
  // Legacy dapp browsers...
  else if (window.web3) {
    console.log('web3, using legacy provider')
    
    window.web3 = new Web3(window.web3.currentProvider);
    
    resolve(window.web3)
  }
  
  // fallback provider
  else if (typeof window.web3 === undefined) {
    console.log('web3, using fallback provider')
    
    window.web3 = new Web3(fallback);
    window.metamask = false;
    
    resolve(window.web3)
  }
  
  // Non-dapp browsers...
  else {
    console.warn('Non-Ethereum browser detected. You should consider trying MetaMask!');
    
    reject()
  }
  
}


export function web3resolver(){
  return new Promise((resolve, reject) => {
    
    // Wait for loading completion to avoid race conditions with web3 injection timing.
    window.addEventListener(`load`, () => resolveWeb3(resolve, reject) )
    
    // resolve immediatly
    if (document.readyState === `complete`) resolveWeb3(resolve, reject)
  })
}