JSFiddle - React, Tailwind, and code Playground

JavaScript

function GroupCollection(items) {
    this.items = items || [];
}

GroupCollection.prototype.myFunction = function() {
    alert(this.items.length);
};

function Selector() {
    this.Status = "";
    this.Groups = new GroupCollection();
    this.Errors = [];
}

Selector.prototype.setGroups = function(groups) {
    this.Groups.items = groups;
};

var selector = new Selector();
selector.setGroups([1,2,3]);
selector.setGroups(['foo', 'bar']);