Function overloading is a feature of object-oriented programming where two or more functions can have the same name but different parameters. When a function name is overloaded with different jobs it is called Function Overloading. In Function Overloading “Function” name should be the same and the arguments should be different.
Unlike other programming languages, JavaScript Does not support Function Overloading.
Example: Here is a small code that shows that JavaScript does not support Function Overloading.
Javascript
function foo(arg1) { console.log(arg1); } /* The above function will be overwritten by the function below, and the below function will be executed for any number and any type of arguments */function foo(arg1, arg2) { console.log(arg1, arg2); } // Driver code foo("Geeks") |
Output:
Geeks undefined
The reason for the “undefined” in the output is: In JavaScript if two functions are defined with the same name then the last defined function will overwrite the former function.
So in this case the foo(arg1) was overwritten by foo(arg1,arg2), but we only passed one
Argument (“Geeks”) to the function. It means that the second argument is undefined, So when we tried to print the second argument, it is printed as “undefined”.
We have seen that function Overloading is not supported in JavaScript, but we can implement the function Overloading on our own, which is pretty much complex when it comes to more numbers and more types of arguments.
Example: The following code will help you to understand how to implement the function Overloading in JavaScript.
Javascript
// Creating a class "foo" class foo { // Creating an overloadable method/function. overloadableFunction() { // Define three overloaded functions var function1 = function (arg1) { console.log("Function1 called with" + " arguments : " + arg1); return arg1; }; var function2 = function (arg1, arg2) { console.log("Function2 called with" + " arguments : " + arg1 + " and " + arg2); return arg1 + arg2; }; var function3 = function (arg1) { var concatenated__arguments = " ", temp = " " // Concatenating all the arguments // and storing them into a string for (var i = 0; i < arg1.length; i++) { concatenated__arguments = concatenated__arguments + arg1[i] } /* Just ignore this loop and temp variable, we are using this loop to concatenate arguments with a space between them */ for (var i = 0; i < arg1.length; i++) { temp = temp + " " + arg1[i] } console.log("Function3 called with this" + " array as an argument : [" + temp + "]"); console.log("Output of log is : ") // Returns concatenated argument string return concatenated__arguments; }; /* Here with the help of the length of the arguments and the type of the argument passed ( in this case an Array ) we determine which function to be executed */ if (arguments.length === 1 && Array.isArray(arguments[0])) { return function3(arguments[0]); } else if (arguments.length === 2) { return function2(arguments[0], arguments[1]); } else if (arguments.length === 1 && !Array.isArray(arguments[0])) { return function1(arguments[0]); } } } // Driver Code // Instantiate an object of the "foo" class var object = new foo(); // Call the overloaded functions using the // function overloadableFunction(...) // We are passing 1 argument so executes function1 console.log(object.overloadableFunction("Geeks")); // We are passing two arguments so executes function2 console.log(object.overloadableFunction("Geeks", "for")); // We are passing an array so executes function3 console.log(object.overloadableFunction( ["Geeks", "for", "Geeks"])); |
Output:
Function1 called with arguments : Geeks Geeks Function2 called with arguments : Geeks and for Geeksfor Function3 called with this array as an argument : [ Geeks for Geeks] neveropen Output of log is : neveropen
Explanation: In the above program, when a different number of arguments are passed to the same function, then based on the number and type of arguments, the arguments will be passed to the respective function.
In this case, we have used three different functions (function1, function2, function3) for function Overloading.
