db error{ "message": "connect ECONNREFUSED ::1:27017" i cant connect with my db

Question

const mongoose = require("mongoose");
mongoose.set("strictQuery", true);
mongoose.connect("mongodb://localhost:27017/", (err) => {
if (!err) {
console.log("  db connected successfully");
 } 
 else {
console.log(" db error" + JSON. stringify (err, undefined, 2));
}
});
module.exports = mongoose;

this is my db.js file I am getting this error

error{
  "message": "connect ECONNREFUSED ::1:27017",
  "reason": {
    "type": "Unknown",
    "servers": {},
    "stale": false,
    "compatible": true,
    "heartbeatFrequencyMS": 10000,
    "localThresholdMS": 15,
    "setName": null,
    "maxElectionId": null,
    "maxSetVersion": null,
    "commonWireVersion": 0,
    "logicalSessionTimeoutMinutes": null
  }
}