How to use this web3.js on browsers without MetaMask (for read-only Ethereum queries):
const web3 = new Web3(window.web3.currentProvider);
window.web3 is undefined.
I think, I can initialize
Web3 by specifying a provider manually. But how to decide what exactly to pass as the argument to
new Web3 (for mainnet and for rinkeby)?
I need to use my own Infura account? Maybe I can pass the MetaMask's account (is it legal? what is the MetaMask provider URLs for mainnet and for rinkeby)?