ethereum geth keystore -> private key -> address (check)

Use keythereum, web3

  
npm install keythereum  
npm install web3  

．datadir need to correct.
UTC/keystore/UTC–2019-03-25T09-10-35.xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
．address need correct “0xooooooooooooooooooooooooo”
．password need correct, this example is empty.
．web3 localhost is fake, don’t need have geth.

  
var keythereum = require("keythereum");  
var datadir = "UTC";  
var address= "0xooooooooooooooooooooooooo";  
const password = "";  
  
var keyObject = keythereum.importFromFile(address, datadir);  
var privateKey = keythereum.recover(password, keyObject);  
console.log(privateKey.toString('hex'));  
  
Web3 = require('web3')  
web3 = new Web3(new Web3.providers.HttpProvider("localhost"));    
var address = web3.eth.accounts.privateKeyToAccount("0x"+privateKey.toString('hex'));  
console.log(address);