how to merge multiple objects in array javascript code example

Example 1: javascript object array merge

var arr1 = [{name: "lang", value: "English"},{name: "age", value: "18"}];
var arr2 = [{name : "childs", value: '5'}, {name: "lang", value: "German"}];

Array.prototype.push.apply(arr1,arr2); 

console.log(arr1);  // final merged result will be in arr1

Example 2: javascript create array of objects from multiple arrays

var ids = [1,2,3]; //Hundreds of elements here
var names = ["john","doe","foo"]; //Hundreds of elements here
var countries = ["AU","USA","USA"]; //Hundreds of elements here

// Create the object array
var items = ids.map((id, index) => {
  return {
    id: id,
    name: names[index],
    country: countries[index]
  }
});

// Result
var items = [
    {id: 1, name: "john", country: "AU"},
    {id: 2, name: "doe", country: "USA"},
    ...
];