<P> Default arguments for member functions may be specified both in declaration and definition . But in order to call such member function with substituted values the definition must be visible before a first call . Example: </P> <P> Some other languages, like Java, do not have default arguments . However, the same behaviour can be simulated by using method overloading to create overloaded methods of the same name, which take different numbers of arguments; and the versions with fewer arguments simply call the versions with more arguments, with the default arguments as the missing arguments: </P> <P> However, in addition to several other disadvantages, since the default arguments are not modeled in the type system, the type of a callback (aka higher - order function) can't express that it accepts either of the overloads nor simulate the default arguments with overloaded functions . Whereas, in JavaScript the non-overloaded function definition can substitute the default when the input value is undefined (regardless if it was implicitly undefined via the argument's absence at the call site or an explicitly passed undefined value); which is modeled as an optional argument parameter type?: in TypeScript . JavaScript's solution is not resolved statically (i.e. not at compile - time, which is why TypeScript models only the optionality and not the default values in the function's type signature) thus incurs additional runtime overhead, although it does provide more flexibility in that callbacks can independently control their defaults instead of centrally dictated by the (callback's type signature in the) type signature of the function which inputs the callback . The TypeScript solution can be simulated in Java with the Optional type except the analogous of an implicit undefined for each absent argument is an explicit Optional. <Integer> absent () at the call site . </P> <P> For every function call default argument values must be passed to the called function . * * This leads to some code bloat - in contrast to function overloads. * * (Comment: Why so? Someone who wrote or understand the previous full sentence please help explain it . Otherwise I think it is the function overloads lead to source code bloat - you would need to write (at least) one extra function signagure rather than just write one more parameter .) (Comment response: the original text appears to maybe allude to languages which implement default arguments duplicated at each call site in the code generated by the language compiler or interpreter (i.e. not referring to the source code which of course overloaded methods can bloat), rather than at the definition site (the choice has tradeoffs either way), per my explanation in the Overloaded methods section .) </P>

When do we need to use default arguments in a function