javascript - Function.apply in connect's source code -

this question has answer here:

• does make sense use .apply( ) , pass same instance context? 2 answers

reading connect's source code, came across following lines. want know why it's using function.apply.

app.listen = function(){   var server = http.createserver(this);   return server.listen.apply(server, arguments); }; 

as understand, function.apply used in cases want call function different this value. since server.listen's this server in above example, isn't sufficient write following?

app.listen = function(){   var server = http.createserver(this);   return server.listen(arguments); }; 

.apply(thisarg, argsarray) takes 2 arguments can see described here. first argument (which sounds know) this value function call. second argument array-like object contains arguments passed function. second argument why being used here can call function same arguments passed first function app.listen().

this common usage "forwarding" arguments 1 function without having know arguments are. since arguments object array-like data structure, fits second argument of .apply() expects array-like object list of arguments.

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server.listen(arguments); not work because call .listen(), passing single argument function array-like list of arguments. not function signature of server.listen(). needs each argument passed separately, not passed in list. .apply() serves purpose of fixing that. takes array-like list of arguments , passes them individual arguments called function.

server.listen(...) further complicated fact has 4 different possible sets of arguments can passed it. use of .apply() allows forwarding code entirely independent of arguments passed forwards passed without having know it.