Merge Arrays in one with ES6 Array spread

gistfile1.txt

const arr1 = [1,2,3]
const arr2 = [4,5,6]
const arr3 = [...arr1, ...arr2] //arr3 ==> [1,2,3,4,5,6]

var odd = [
    { name : "1", arr: "in odd" },
    { name : "3", arr: "in odd" }
];

var even = [
    { name : "1", arr: "in even" },
    { name : "2", arr: "in even" },
    { name : "4", arr: "in even" }
];

// ----
// ES5 using Array.filter and Array.find
function merge(a, b, prop){
  var reduced = a.filter(function(aitem){
      return ! b.find(function(bitem){
          return aitem[prop] === bitem[prop];
      });
  });
  return reduced.concat(b);
}
console.log( "ES5", merge(odd, even, "name") );

// ----
// ES6 arrow functions
function merge(a, b, prop){
    var reduced =  a.filter( aitem => ! b.find ( bitem => aitem[prop] === bitem[prop]) )
  return reduced.concat(b);
}
console.log( "ES6", merge(odd, even, "name") );

// ----
// ES6 one-liner
var merge = (a, b, p) => a.filter( aa => ! b.find ( bb => aa[p] === bb[p]) ).concat(b);


console.log( "ES6 one-liner", merge(odd, even, "name") );

// Results
// ( stuff in the "b" array replaces things in the "a" array )
// [
//    {
//         "name": "3",
//         "arr": "in odd"
//     },
//     {
//         "name": "1",
//         "arr": "in even"
//     },
//     {
//         "name": "2",
//         "arr": "in even"
//     },
//     {
//         "name": "4",
//         "arr": "in even"
//     }
// ]