javascript - When are variables evaluated when passing them into functions? -

this simple question, know answer.

are arguments passed function calculated once , set local variables or calculated every time they're used inside function?

for example:

when write forloop, should set variable finds object using iteration:

  for(var = 0; < objects.length; i++) {      var obj = objects[i];      obj.title = "title";      obj.description = "description";   } 

if don't set obj variable operation finding object run more once:

  for(var = 0; < objects.length; i++) {      objects[i].title = "title";      objects[i].description = "description";   } 

so far i've learnt bad (although i'm guessing performance difference in modern browsers unnoticeable).

my question is, if wrapped modifying methods in function , passed objects[i] function, objects[i] calculated once , set local variable obj in function or calculate every time obj called?

what better practice, code or code b?

code a:

   function modify(obj) {       obj.title = "title";       obj.description = "description";    }     (var = 0; < objects.length; i++) {       modify(objects[i]);    } 

code b:

   function modify(obj) {       obj.title = "title";       obj.description = "description";    }     (var = 0; < objects.length; i++) {       var obj = objects[i];       modify(obj);    } 

update: question similar different this question because questions when value calculated rather value passed.

my question is, if wrapped modifying methods in function , passed objects[i] function, objects[i] calculated once , set local variable obj in function?

yes. once value passed, it's passed. doesn't recompile argument each time.

therefore, code "better", doubt makes of difference @ all....