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See following example;

You could skip the ternary, and evaluate the “not not x”, e.g. !!x.

If x is undefine, !x is true, so !!x becomes false again. If x is true !x is false so !!x is true.

function logBool(x) {
    x = !!x;
    console.log(x);
}

var a, b = false, c = true;
logBool(a); // false
logBool(b); // false
logBool(c); // true

https://stackoverflow.com/questions/24332839/set-a-default-value-for-a-boolean-parameter-in-a-javascript-function

An “empty” function in JavaScript is one that has no statements or executable code inside of its function body. Empty functions can be helpful as placeholders for future-implemented functions or as default functions to avoid errors if a function call is made when no action is needed.

What are Empty Functions in JavaScript?

A function that has no statements or instructions inside of its body is said to be an “empty function” in JavaScript. For defining an “empty function”, the “function” keyword, empty pair of parentheses, and an empty pair of curly braces are used.

How to Define Empty Functions in JavaScript?

The following syntax is utilized for creating an empty function:

function emptyFunction() {

// no statement or instructions

}

Or

const emptyFunction = () => {

// no statement or instructions

};

Use Case Scenarios of Empty Functions in JavaScript

Empty functions can be useful in various situations, such as:

• Developers may want to define a function but do not yet have an actual implementation. So, they have to use the empty function as a placeholder and then add the implementation details later.
• Sometimes, developers need a function that does nothing while defining event handlers for elements. So, they utilize the empty function as a placeholder for the element’s event attribute until the actual functionality is not added.
• While defining an object, developers may want to include a default function as one of the properties of the object. For this, an empty function can be utilized as a temporary replacement for the default function until it is replaced with a new implementation.

Example: Add Empty function to Handle Event

Here, we will handle the click event of the button using the empty function as a placeholder that will be implemented later for any specific task.

First, define an empty function “buttonClick()” to handle the button’s click event:

function buttonClick() {}

Now, access the button by getting its reference using the assigned id:

const button = document.getElementById("btn");

Then, assign the empty function “buttonClick()” to the click event of the button:

button.onclick = buttonClick;

The above code helps to handle the click event to avoid errors.

I’m just wondering about what the lines ‘function Animal() { }’ and ‘function Bird() { }’ are for when the functions are wrapping anything?

function Animal() { }
Animal.prototype.eat = function() {
  console.log("nom nom nom");
};
function Bird() { }
Bird.prototype = Object.create(Animal.prototype);
Bird.prototype.constructor = Bird;

Think of Animal as the pattern, the “blueprint” used to create each instance of Animal. Defining the function of telling Javascript what to do when we say

const octopus = new Animal();

The function simply defines the shape of that new thing, the instance of our constructor. An empty function creates an empty object (no properties) that is wired to the constructor’s prototype. Doing this, the instance can use any of those prototype methods or properties.