I try to load the Metamask Web3 object into my nuxt.js frontend. On page load i encounter the following error:

Error: The MetaMask Web3 object does not support synchronous methods like eth_mining without a callback parameter. See https://github.com/MetaMask/faq/blob/master/DEVELOPERS.md#dizzy-all-async---think-of-metamask-as-a-light-client for details.
    at MetamaskInpageProvider.send (inpage.js:1)
    at RequestManager.webpackJsonp../node_modules/web3/lib/web3/requestmanager.js.RequestManager.send (requestmanager.js:58)
    at Eth.get [as mining] (property.js:107)
    at e (backend.js:1)
    at e (backend.js:1)
    at backend.js:1
    at Object.t.b (backend.js:1)
    at stringify (backend.js:1)
    at Object.e.on.e (backend.js:1)
    at Object.emit (<anonymous>:1:532)

Here is the relevant code:

export const state = () => ({
  contractInstance: null

export const mutations = {
  registerContractInstance (state, payload) {
    console.log('contract instance: ', payload)
    state.contractInstance = () => payload

export const actions = {
  getContractInstance ({commit}) {
    getContract.then(result => {
      commit('registerContractInstance', result)
    }).catch(err => {
      ====================error catch in here(contract.js:27 )

getContract code:

let getContract = new Promise(function (resolve, reject) {
  if (typeof web3 !== 'undefined') {
    // Use MetaMask's provider
    web3 = new Web3(web3.currentProvider)
  } else {
    web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"))
  let contract = web3.eth.contract(abi)
  let contractInstance = contract.at(address)

export default getContract

my environment : "web3 ^0.20.0"

2 Answers 2


I had a similar problem and found this very helpful. https://github.com/ethereum/wiki/wiki/JavaScript-API#using-callbacks

web3.eth.getBlock(48, function(error, result){

You need to store your contractInstance as a function

Check out part 2 of my tutorial which uses VueJS: https://itnext.io/create-your-first-ethereum-dapp-with-web3-and-vue-js-part-2-52248a74d58a

check out getWeb3() and the registerWeb3 action and mutations.

It's pretty stupid so I use ethersjs now. Little less documentation but a way more readable API that works extremely well to work without metamask as it splits provider and wallet so that we only send signed transactions from our light client to a full node and never expose our privkey.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.