{
    "connections": {
        "<my_username>": {
            "accessToken": "<my_accessToken>",
            "instanceUrl": "<https://my.partial.instance.com>",
            "client": "default"
        }
    },
    "clients": {
        "default": {
            "clientId": "<myclientid>",
            "clientSecret": "<longNumber>",
            "redirectUri": "https://localhost:1111",
            "loginUrl": "https://test.salesforce.com"
        }
    }
}

var jsforce = require('jsforce');
var conn = new jsforce.Connection({
  oauth2 : {
    // you can change loginUrl to connect to sandbox or prerelease env.
    loginUrl : 'https://test.salesforce.com',
    clientId : '<myclientid>',
    clientSecret : '<longNumber>',
    redirectUri : '<https://my.partial.instance.com>'
  }
});
conn.login(username, 'password'+'<id>', function(err, userInfo) {
  if (err) { return console.error(err); }
  // Now you can get the access token and instance URL information.
  // Save them to establish connection next time.
  console.log(conn.accessToken);
  console.log(conn.instanceUrl);
  // logged in user property
  console.log("User ID: " + userInfo.id);
  console.log("Org ID: " + userInfo.organizationId);
  // ...
});