string typeError: variable is undefined

Question

I am writing a little program with javascript and html canvas. It is my first javascript program. It will make the dragonCurve thing. But I am getting this error:TypeError: old is undefined. I am not the first one with this question but after reading the other questions I still couldn't find a solution.

The following code is part of the program where it raises an error. So why does it give an error?

<script>
var r = 'r';
var l = 'l';

var old = r;
var newer = old;

var iteration = 10;
var cycle = 1;

while (cycle < iteration){
  newer = (old) + (r);
  old = old.reversed;

  var oldstring = old.split("");  <!-- here is the error -->

  cycle++;
}
</script>

I can't reproduce that error from the code you posted, but I do get one about iteration being undefined. — j08691
– j08691, Commented Feb 25, 2016 at 20:16
my bad there also needs to be var iteration = 20; at the top of the code — Tristan
– Tristan, Commented Feb 25, 2016 at 20:18
@BarryDoyle I changed my post. And yea there is cycle++ at the end (and inside) of the while loop. — Tristan
– Tristan, Commented Feb 25, 2016 at 20:22
@BarryDoyle old.reverse should reverse the old string. So the first letter of old will be the last etc. — Tristan
– Tristan, Commented Feb 25, 2016 at 20:25

Barry Michael Doyle · Accepted Answer · 2016-02-25 20:28:33Z

1

"reversed" isn't a default function in JavaScript.

You'll need to create and add a function like this one:

function reverse(s){
  return s.split("").reverse().join("");
}

Then replace old = old.reversed; with old = reverse(old);

This should solve the problem.

answered Feb 25, 2016 at 20:28

Barry Michael Doyle

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2 Comments

Barmar Over a year ago

he's not even calling reverse as a function, he's using it as a property.

sqykly Over a year ago

Final thing: you may want to clarify what you mean by "default function"

Barry Michael Doyle · Accepted Answer · 2016-02-25 21:14:02Z

0

Yeah so if he really wanted to he could also just say old.reversed ();

answered Feb 25, 2016 at 21:14

Barry Michael Doyle

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2 Comments

sqykly Over a year ago

reverse() not reversed(), and you really should edit your already accepted answer instead of writing another - especially in this case because this is a better answer (provided you fix the function name)

sqykly Over a year ago

It happens. Mobile is really bad for SO, it doesn't get the context at all.

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