Overloading

Overloading: which is the ability of a single function to have multiple signatures.

A function signature is made up of the function name plus the number and type of parameters the function expects
As mentioned previously, JavaScript functions can accept any number of parameters, and
the types of parameters a function takes aren’t specified at all.

That means JavaScript functions don’t actually have signatures. A lack of function signatures also means a lack of function overloading. Look at what happens when you try to declare two functions with the same name

(see next code running here -> https://playcode.io/664865)

function sayMessage(message) {
 console.log(message);
}

function sayMessage() {
 console.log("Default message");
}

sayMessage("Hello!");    // outputs "Default message"

In JavaScript, however, when you define multiple functions with the same name, the one that appears last in your code wins. The earlier function declarations are completely removed, and the last is the one that is used. Once again, it helps to think about this situation using objects:

var sayMessage = new Function("message", "console.log(message);");
sayMessage = new Function("console.log(\"Default message\");");
sayMessage("Hello!"); // outputs "Default message"

Overloading

References