structobject._childElements.push(element);

You're trying to modify the (non-existent) _childElements property of the Constructor function instead of the instance you created with new structobject.

Use this instead of structobject on that line.

It is conventional, in JavaScript, to use variables starting with capital letters for constructor functions.

var structobject = function(...) {

would be better written as:

var Structobject = function(...) {

or (since it is a constructor that makes objects):

var Struct = function(...) {

or (because named functions are easier to deal with in debuggers):

function Struct (...) {

Check out Javascript's Array API for details on the exact syntax for Array methods. Modifying your code to use the correct syntax would be:

var array = [];
calendars.forEach(function(item) {
    array.push(item.id);
});

console.log(array);

You can also use the map() method to generate an Array filled with the results of calling the specified function on each element. Something like:

var array = calendars.map(function(item) {
    return item.id;
});

console.log(array);

And, since ECMAScript 2015 has been released, you may start seeing examples using let or const instead of var and the => syntax for creating functions. The following is equivalent to the previous example (except it may not be supported in older node versions):

let array = calendars.map(item => item.id);
console.log(array);

You need to push a newly created item to your array like below:

CoinArray.push(new Coin.Create('123)); 

On the other hand if you want to create an object with keys ids and values corresponding Coin objects, you should try this:

CoinDictionary = {};
CoinDictionary['123'] = new Coin.Create('123');

Note:

I think that you should refactor a bit the Coin if you want to use it as a constructor function:

function Coin(id){
    this.id = id;
}

Doing this change you can use it as below:

CoinArray.push(new Coin('123'));

function Coin(id){
    this.id = id;
}

var CoinArray = [];
CoinArray.push(new Coin('123'));
CoinArray.push(new Coin('456'));
CoinArray.push(new Coin('789'));

console.log(CoinArray);

Update

At the end I want to have array with object and for example I will take first el of array, and execute other method from Coin class.

For this purpose If I were you I would have gone with the creation of an object with keys the ids and values references to Coin objects:

function Coin(id){
    this.id = id;
}

Coin.prototype.start = function(){
    console.log("game with id "+this.id+" started.");
}

Coins = {}
Coins['123'] = new Coin('123');
Coins['456'] = new Coin('456');
Coins['789'] = new Coin('789');

Coins['456'].start();

You can use Array.forEach

var myArray = ['1','2',3,4]

myArray.forEach(function(value){
  console.log(value);
});

a simple solution:

const client_id = "system1";
const device_list = ['dev1' , 'dev2' , 'dev3']

const result = device_list.map(device => [client_id, device]);

The map method is part of the array prototype.

It loops through every item in an array, and applies the given callback to each item.

For more information, I find the Mozilla docs extremely useful!: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map

Another thing to note: map is NON-mutative, meaning it doesn't affect the array on which it is called, it only returns a new one

For..in is used to loop through the properties of an object, it looks like you want to loop through an array, which you should use either For Of, forEach or For

for(const val of rooms) {
    console.log(val)
}