The next method we will implement is the size method (which returns how many elements are in the set). There are three ways of implementing this method.
The first method is to use a length variable and control it whenever we use the add or remove method, as we used in the LinkedList, Stack, and Queue classes in the previous chapters.
In the second method, we use a built-in method from the Object class in JavaScript (ECMAScript 2015+), as follows:
size() {
return Object.keys(this.items).length; // {1}
};
The Object class in JavaScript contains a method called keys that returns an array of all the properties of a given object. In this case, we can use the length property of this array ({1}) to return how many properties we ...
