Portable Web3 Utils. Depends on Truffle Contract.

web3-utils.js

const web3utils = (function() {
  /**************************************
  * Web3
  **************************************/
  const getWeb3 = (fallbackURL = 'http://localhost:8545', web3 = window.web3) => {
    if (web3 !== undefined) {
      web3 = new Web3(web3.currentProvider);
    } else {
      if (fallbackURL && typeof fallbackURL === 'string' && fallbackURL.length > 0) {
        web3 = new Web3(new Web3.providers.HttpProvider(fallbackURL));
      }
    }
    if (!web3) console.log('no web3 injected, no fallback URL provided');
    window.web3 = web3;
    return web3;
  };
  const setWeb3 = (url = 'http://localhost:8545') => {
    web3 = new Web3(new Web3.providers.HttpProvider(url));
    window.web3 = web3;
    return web3;
  };
  /**************************************
   * Get Network
   **************************************/
  const getNetwork = (web3 = window.web3) => new Promise((resolve, reject) => {
    if (!web3) {
      console.log('No web3 instance provided');
      return;
    }
    let id, name;
    web3.version.getNetwork((err, networkId) => {
      if (err) {
        reject(err);
        return;
      }
      id = parseInt(networkId);
      switch (id) {
        case 1:
          name = 'mainnet';
          break;
        case 2:
          name = 'morden';
          break;
        case 3:
          name = 'ropsten';
          break;
        case 4:
          name = 'rinkeby';
          break;
        default:
          name = 'localhost';
      }
      console.log('The network is:', name, id);
      resolve({ id, name });
    });
  });
  /**************************************
   * Get Accounts (with promise)
   **************************************/
  const getAccounts = (web3 = window.web3) => new Promise((resolve, reject) => {
    if (!web3) reject('No web3 instance provided');
    //checking for accounts, keep track of attempts
    let accounts, attempts = 0;
    //limit attempts
    const limit = 5;
    //check function
    const check = () => {
      accounts = web3.eth.accounts;
      if (accounts.length > 0) {
        resolve(accounts);
      }
      else {
        attempts++;
        if (attempts === limit) {
          reject('accounts could not be found on web3 provider');
          return;
        }
        setTimeout(check, 200); //found no accounts, below attempt limit, check again
      }
    };
    check();
  });
  /**************************************
   * Get Contract
   **************************************/
  const getContract = (json, address, web3 = window.web3) => {
    const contract = TruffleContract(json);
    contract.setProvider(web3.currentProvider);
    return address ? contract.at(address) : contract.deployed();
  };
  /**************************************
   * Deploy Contract
   **************************************/
  const deployContract = (json, from, gas) => {
    const contract = TruffleContract(json);
    contract.setProvider(web3.currentProvider);
    contract.new({
      from,
      gas
    });
  };
  /**************************************
   * Exports
   **************************************/
  return {
    getWeb3,
    setWeb3,
    getNetwork,
    getAccounts,
    getContract,
    deployContract
  };
})();