Web3.js: Error: Provider not set or invalid

[pannous]

Could you preconfigure a default provider for noobs?
var web3 = new Web3(web3.currentProvider); doesn't help

[pannous]

web3.setProvider(new web3.providers.HttpProvider()); did it

[keepchen]

var web3 = new Web3(); web3.setProvider(new Web3.providers.HttpProvider("http://localhost:8545"));
Don't forget to run testrpc.
Wish helpful with you.

[keepchen]

At first,you should be run testrpc as a server.Then ｀Web3.providers.HttpProvider("http://localhost:8545"));｀is available.

[utgarda]

const web3 = new Web3(Web3.givenProvider);

gets you wherever Metamask is connected at the moment.