6

When a user changes to a different account in metamask, is there a way to detect it asynchronously in code?

I currently use

this.web3.eth.getAccounts((err, accs) => {   
  this.account = accs[0];
});  

but when the account is changed, it still picks up the previous one. Refreshing the page is not a way to go. Did anyone face this and has a solution?

  • Unfortunately, the method most people used is polling for changes using setIntervals. The only other option is checking if accounts match before each call. – ReyHaynes Mar 15 '18 at 12:50
9

As suggested by Metamask FAQs this might be an option:

var account = web3.eth.accounts[0];
var accountInterval = setInterval(function() {
  if (web3.eth.accounts[0] !== account) {
    account = web3.eth.accounts[0];
    updateInterface();
  }
}, 100);

edit

In the newer version metamask exposes an events that could be used to detect whether there's an account change as per new doc

window.ethereum.on('accountsChanged', function (accounts) {
  // Time to reload your interface with accounts[0]!
})
  • Unfortunately at the moment, checking in a loop is the only supported method. – DanF Mar 15 '18 at 16:29
  • Be careful though, I had a problem where I was always matching the if condition because the account I get was always lowercase. – Antoine Delia Jul 19 '18 at 14:14
  • I use and suggest to use onFocus event to handle this issue. – Vanja Dev Jul 13 at 18:39
22

Using web3 version 1.0.0, the metamask provider exposes an 'update' event you can listen to on it's publicConfigStore.

web3.currentProvider.publicConfigStore.on('update', callback);

Your callback will be passed an object with 'selectedAddress' and 'networkVersion' whenever those attributes change.

  • 2
    Hi Brian, where can I find documentation about the update event? Have searched the web3 1.0 docs. Thanks. – Vindberg Nov 23 '18 at 19:38
9

From new metamask docs:

https://metamask.github.io/metamask-docs/Advanced_Concepts/Provider_API#ethereum.on(eventname%2C-callback)

window.ethereum.on('accountsChanged', function (accounts) {
  // Time to reload your interface with accounts[0]!
})

window.ethereum.on('networkChanged', function (netId) {
  // Time to reload your interface with netId
})

you can also prevent metamask from automatically reloading web page

window.onbeforeunload = function() {
  return "Prevent reload"
}

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