Adding values to an array that is local to a function without modifying the function itself

Question

function animal(){
  var species = new Array('Monkey', 'Dog', 'Cat');
  for(i=0;i<species.length;i++)
  {
    document.writeln(species[i]);
  }
}

How can I add another value to the species array without modifying the animal() function?

"without change the script within the function"... that's not going to be possible. Why can you not change the function? — James Allardice
– James Allardice, Commented Jul 15, 2012 at 16:25

Darin Dimitrov · Accepted Answer · 2012-07-15 16:25:06Z

1

It's impossible to add values to the array without changing the code of this function for the simple reason that the species variable used there is a local variable declared within the scope of the function. So this variable is not visible to outside code. In addition to that the values of this array are hardcoded. So forget about it. Impossible without touching at the function implementation.

answered Jul 15, 2012 at 16:25

Darin Dimitrov

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2 Comments

Ega Rana Over a year ago

There's another way to change it?

Darin Dimitrov Over a year ago

Yes, of course. If you change the implementation of this function you could add whatever values you want to the array. The array could also be passed as argument. This way the caller of the function could provide his own array of values.

Christian · Accepted Answer · 2012-07-15 16:29:09Z

1

I'm not sure I fully understand your concerns, but javascript unlike some other languages can entirely overwrite a function.

So, assuming the above code, I could do:

window.animal = function(){
  var species = new Array('Monkey', 'Dog', 'Cat', 'Mouse', 'Fish');
  for(i=0;i<species.length;i++)
  {
    document.writeln(species[i]);
  }
}

That said, I would avoid the use of document.writeln(), I consider that function worse than eval()... Also, as Darin hinted, I would also not define data local to a function if at all possible.

answered Jul 15, 2012 at 16:29

Christian

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2 Comments

Simon Forsberg Over a year ago

Why do you consider writeln worse than eval?

Christian Over a year ago

You can get around bad code written in eval(), but not so much with writeln(). I had a particular case in Joomla where it used writeln() to write html to the document. My template got the script through AJAX and when it got executed, I kept getting a blank page with the written HTML (since writeln() clears the page when called after the document loads).

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