Fallback function in web3

Question

I find answer how to make upgradable contract here

How to call function from currentVersion with fallback function on web3?

    contract Relay {
    address public currentVersion;
    address public owner;

    function Relay(address initAddr){
        currentVersion = initAddr;
        owner = msg.sender;
    }

    function update(address newAddress){
        if(msg.sender != owner) throw;
        currentVersion = newAddress;
    }

    function(){
        if(!currentVersion.delegatecall(msg.data)) throw;
    }
}

Answer 1

You can do this with the sendTransaction function, like so:

web3.eth.sendTransaction({
  from: sendingAccount,
  to: contract.address,
  data: yourData, // optional, if you want to pass data or specify another function to be called by delegateCall you do that here
  gas: requiredGas, // technically optional, but you almost certainly need more than the default 21k gas
  value: value //optional, if you want to pay the contract Ether
});

Answer 2

You probably don't need it anymore, but you can retype the Relay address to instance contract:

contract Instance{
   function doSomething(){ ... }
}

and then if Relay.deployed() is at address 0x12345678, do:

in = Instance.at('0x12345678')
in.then(function(i){ i.doSomething(); })