web3.js Error: the method personal_listAccounts does not exist/is not available [duplicate]

Question

• Code:

  var Web3 = require('web3');
  var web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));
  
  
  var sender = web3.eth.accounts[0];
  console.log('Sender: ' + sender);
  
  web3.personal.listAccounts;
  

• Output:

  Sender: 0xA0A0A01
  
  
  home/ubuntuuser/node_modules/web3/lib/web3/requestmanager.js:61
      throw errors.InvalidResponse(result);
      ^
  Error: The method personal_listAccounts does not exist/is not available
  at Object.module.exports.InvalidResponse (/home/ubuntuuser/node_modules/web3/lib/web3/errors.js:38:16)
  at RequestManager.send (/home/ubuntuuser/node_modules/web3/lib/web3/requestmanager.js:61:22)
  at Personal.get [as listAccounts] (/home/ubuntuuser/node_modules/web3/lib/web3/property.js:107:62)
  at Object.<anonymous> (/home/ubuntuuser/Desktop/Ethereum/ethy.js:63:14)
  at Module._compile (module.js:410:26)
  at Object.Module._extensions..js (module.js:417:10)
  at Module.load (module.js:344:32)
  at Function.Module._load (module.js:301:12)
  at Function.Module.runMain (module.js:442:10)
  at startup (node.js:136:18)
  

---

• Question:

From the above, commands like web3.eth.accounts[0] works fine, however web3.personal.listAccounts; doesn't. Why might that be the case?