object convert into unique key js

const _ = require("lodash");

// The source object
var info = [
   { 'user': 'amit', 'age': 23 },
 { 'user': 'priya', 'age': 21 },

 { 'user': 'priya', 'age': 25 },
];

// Using the _.mapKeys() method
 const newInfo=_.mapKeys(info,
  function(o) { return o.age; })


 console.log('info',newInfo["25"]);