On Apr 12, 2012, at 8:38 PM, Russell Leggett wrote:
>
>
> At first the answer to this didn't really matter to me, because how often
> does someone pass undefined to a function like foo(undefined). I know I
> don't, though I'm sure it happens occasionally. Then I thought about it and
> realized that it happens in my code all the time, just not like that. A much
> more common case is a pass through of an argument to another function.
>
> function fadeIn(duration=200){...}
> function fadeOut(duration=200){...}
> function fadeToggle(duration){
> if(visible){
> fadeOut(duration);
> }else{
> fadeIn(duration);
> }
> }
>
> Here, the argument duration is always passed through fadeToggle to fadeIn or
> fadeOut. Someone writing fadeIn would always expect to have a default of 200.
> fadeToggle does not care about the duration so much as it wants to pass it on
> and use the defaults of the functions it calls. If passing undefined does not
> trigger the default, it would have to be rewritten like:
>
> function fadeToggle(duration){
> var hasDuration = typeof duration != "undefined";
> if(visible){
> if(hasDuration){
> fadeOut(duration);
> }else{
> fadeOut();
> }
> }else{
> if(hasDuration){
> fadeIn(duration);
> }else{
> fadeIn();
> }
> }
> }
I'd write it:
function fadeToggle(...args){
if(visible){
fadeOut(...args);
}else{
fadeIn(...args);
}
}
If you don't care about the the actual argument values are just passing them on
that's how you should do it.
Allen
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