JSFiddle - React, Tailwind, and code Playground

by Alexey

JavaScript

let fruits = [
  { Id: 1, Name: 'Apple' }, 
  { Id: 2, Name: 'Pear' },
  { Id: 3, Name: 'Orange' }, 
  { Id: 4, Name: 'Plum' }, 
  { Id: 5, Name: 'Cherry' }
];
let selected = [{Id: 3, Name: 'Orange'}];

function addUniqueIds(src, dst) {
  var lookup = {};
  for (var i = 0; i < dst.length; i++) {
    lookup[dst[i].Id] = true;
    console.log(lookup)
  }  
  for (var i = 0; i < src.length; i++) {
    if (!lookup[src[i].Id]) {
      lookup[src[i].Id] = true;
      dst.push(src[i]);
    }
  }
}

addUniqueIds(fruits, selected);
console.log(selected.length, selected);