Question

I know of two methods of setting a default parameter, but I would like to know what the preferred method is.

function Foo(par1, par2) {     if(par2 == null)         par2 = 'my default' } 

or

function Foo(par1, par2) {     par2 = par2 || 'my default' } 

or is there a better way than either of these?

EDIT:

I would also like to know how others handle multiple optional parameters such as this: We have several functions like this in internal libraries (I think they’re pretty ugly).

function Foo(par1, par2, par3) {     if(par2 == null)         par2 = 'my default'     if(par3 == null)         par3 = 'my default'     // Do something } 

And to call it:

Foo('Parameter one',null,true) 

Answer 1

Personally I think the second form is just outright cleaner and more readable, certainly moreso than sergey’s arguments inspection – though that can have it’s place – but I prefer to pass extensible objects for args than have to maintain arg signatures.

e.g.

function Foo(myArgs) {     myArgs.par1 = myArgs.par1 || 'my default'     myArgs.par2 = myArgs.par2 || 'my default' }