Subj : spidermonkey bug or feature? watch on array.length
To   : netscape.public.mozilla.jseng
From : Jens Thiele
Date : Thu Aug 26 2004 08:21 pm

What I want to do:
call a function each time an element is added to an array

example:
f=function(p,o,n){
  println("this[p]:"+this[p]+" p:"+p+" o:"+o+" n:"+n);return n;
};

a=[];
a.watch("length",f);
a[0]=10;

will print:
this[p]:0 p:length o:0 n:1

a=[];
a.watch("length",f);
a.push(10);

will print:
this[p]:0 p:length o:0 n:1
this[p]:1 p:length o:1 n:1

=> my function is called twice

bug or feature?

the nice feature of the "second version" is you are called again after
the element is added which allows you to inspect the added element

Jens

.