Update JavaScript Object in Collection

updateCollectionArray.js

let startTime = new Date();
// updating an object in a array/collection
let collection = [
  {id:3, name:"Item #1",age:32},
  {id:4, name:"Item #2",age:33},
  {id:5, name:"Item #3",age:34},
  {id:6, name:"Item #4",age:35},
  {id:7, name:"Item #5",age:36},
  {id:8, name:"Item #6",age:47},
];

function assign(o,replace) {
  Object.keys(o).map(function(key) {
    if (replace[key] !== undefined) { 
      o[key] = replace[key]; 
    } else { 
      o[key] = o[key];
    }
  });
  return o;
}

function updateObj(collection, id, replacement) {
   return collection.map(function (o) {
     return o.id === id ? assign(o,replacement) : o;
   });
}

console.log(collection);
let newCollection = updateObj(collection, 6, {name: "Demo Hello"});
console.log(newCollection);

let newCollection2 = updateObj(collection, 3, {age: 87});
console.log(newCollection2);

console.log('It took ' + new Date() - startTime + ' milliseconds to calculate.');