let first = [ {name: 'Maxim', secondName: 'Ivanov'}, {name: 'Lena', secondName: 'Kirolova'} ]
let second = [ {age: 20}, {age: 18} ]
//// Результат должен быть таким
[ { name: 'Maxim', secondName: 'Ivanov', age: 20 }, { name: 'Lena', secondName: 'Kirolova' , age: 18 } ]
var alpha = ['a', 'b', 'c'],
numeric = [1, 2, 3];
var alphaNumeric = alpha.concat(numeric);
console.log(alphaNumeric); // Результат: ['a', 'b', 'c', 1, 2, 3]