var Web3 = require('web3');

// connect to TrueChain network
var web3 = new Web3('http://localhost:8545', 'etrue')
web3.eth.net.getBlockNumber().then(console.log)
// print: block number

console.log(web3.currentProvider.type)
// print: "etrue"

// switch network type
// incorrect network correspondence can cause methods to fail!
web3.setProvider('http://localhost:8545', 'eth')
web3.eth.net.getBlockNumber().then(console.log)
// Returned error: The method eth_blockNumber does not exist/is not available

console.log(web3.currentProvider.type)
// print: "eth"