Function Overloading in JavaScript

Function Overloading is a feature found in several object-oriented programming languages, which permits multiple functions to share the same name but vary in the number or type of parameters. Although native support for function overloading exists in languages like C++ and Java, it does not exist natively in JavaScript.

In JavaScript, when the same name is given to more than one function, it replaces all previous functions with the most recently defined function. It is so because JavaScript treats a function as an object, and so when it redefines a new function with the same name, it just replaces the reference for that function.

Note: This is one aspect where JavaScript does not support Function Overloading.

Example: This is a short code snippet that shows that JavaScript does not support Function Overloading.

Code

Output

JavaScript natively does not support function overloading. In the above code, the second function definition, foo(arg1, arg2), overrides the first definition, foo(arg1). When foo("Geeks") is called, the version with two arguments is called, but the second argument is not defined because there is only one argument passed to it. JavaScript natively doesn't support function overloading; however, function overloading can be implemented through a custom function, which is very complex while handling multiple arguments and different data types.

Example: This is an example which brings out the process of function overloading by a program in JavaScript.

Code

Output

In the above program, when different numbers of arguments are passed to the same function, the argument will be passed to the correct function based on the number as well as the type of the arguments. In this example, we have used three different functions, function1, function2, and function3 for representing function overloading.

Conclusion

It is worth mentioning that JavaScript, by its nature, does not support function overloading like C++ or Java do. However, we can somewhat mimic function overloading by using techniques such as the arguments object, rest parameters, or type verification to check for the number of arguments or the types of arguments.