Function in an object in JavaScript

Using symbols, functions can be added to objects and these functions will not participate in the looping. Let's try. Let's have an object:

javascriptlet obj = {a: 1, b: 2, c: 3};

Let's create a symbol:

javascriptlet sym = Symbol();

Write a function to an object with a key in the form of our symbol:

javascriptobj[sym] = function() {
  console.log('!!!');
};

When iterating over the object, our function will not be iterated:

javascriptfor (let key in obj) {
  console.log(obj[key]); // 1, 2, 3
}

We get our function by passing our symbol (the same variable) as a key:

javascriptlet func = obj[sym];
func();

We can shorten the code:

javascriptobj[sym]();