Unable to work with web3.js on geth

Question

This is my code:

   function send() {
    Web3.providers.HttpProvider.prototype.sendAsync = Web3.providers.HttpProvider.prototype.send;
    var web3 = new Web3("http://localhost:8545");
    var data = web3.eth.getHashrate();
    alert(data);
}

when i run the send() function I am getting this error: "TypeError: this.provider.sendAsync is not a function"

Answer 1

The default websocket port is 8546

You could try

var web3 = new Web3("ws://localhost:8546");

Or connecting to the HTTP JSON RPC

var web3 = new Web3("http://localhost:8545");

Answer 2

I think here is a similar issue on github https://github.com/ethereum/web3.js/issues/1119

the idea is to use

Web3.providers.HttpProvider.prototype.sendAsync = Web3.providers.HttpProvider.prototype.send

before creating new instance. Besides, as spoted by @cleanunicorn you should set the default ws port 8546 unless you have defined it differently when you've runed geth.

This error might be caused by a connection problem so run geth with the following options

--ws --wsport 8546 --wsaddr "0.0.0.0" --wsorigins="*"