# Just a little help

**URL:** <https://discourse.processing.org/t/just-a-little-help/28768>\
**Category:** Coding Questions\
**Created:** [March 23, 2021, 5:55pm UTC](https://discourse.processing.org/t/just-a-little-help/28768 "2021-03-23T17:55:20Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![cjswinter](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/cjswinter/32/12518_2.png) [@cjswinter](https://discourse.processing.org/u/cjswinter)\
**Post date:** [March 23, 2021, 5:55pm UTC](https://discourse.processing.org/t/just-a-little-help/28768/1 "2021-03-23T17:55:21Z")

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Hi, sorry but would someone be able to explain why this code runs fine 7 times in a row and then fails on the 8th. Nothing changes.  
This is almost certainly not the correct way to code this, but I am still learning.  
Thanks, and apologies if this is really stupid.

[https://editor.p5js.org/cjstanleywinter/sketches/TKADWBYMT](https://editor.p5js.org/cjstanleywinter/sketches/TKADWBYMT)

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**Author:** ![TfGuy44](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/tfguy44/32/41_2.png) [@TfGuy44](https://discourse.processing.org/u/TfGuy44)\
**Post date:** [March 23, 2021, 6:59pm UTC](https://discourse.processing.org/t/just-a-little-help/28768/2 "2021-03-23T18:59:37Z")

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Your sketch keeps calling `currentScreen++;`, so the value in `currentScreen` keeps going up.

This is, essentially, what moves the narrative along.

But then you also do this:

```auto
let sentences = narrative.screens[currentScreen].sentences;

```

This works fine for the first screen, and the second, and a few more.  
But eventually it runs into a problem  
See, the array `narrative.screens` has a fixed size. One that `currentScreen` will eventually exceed. And at that point, you’re trying to access an array element that isn’t there. And that’s a problem.

* * *

The issue is similar to this. Here’s my shopping list:

```auto
/// SHOPPING LIST:
0) Milk.
1) Eggs.
2) Sugar.
3) Carrots.
4) Ham.

```

If I asked you for item #0 on the list, you can tell me easily: Milk.

If I asked for item #3 on the list: Carrots.

Clearly this is a list of five things. So what’s the #5 item on this list?

PROBLEM.

The list might be 5 things long, but there’s no #5 item on the list!

Your code is running into exactly the same issue. Except your shopping list is `narrative.screens` and the item number is `currentScreen`.

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<div class="post-metadata">

**Author:** ![cjswinter](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/cjswinter/32/12518_2.png) [@cjswinter](https://discourse.processing.org/u/cjswinter)\
**Post date:** [March 23, 2021, 7:59pm UTC](https://discourse.processing.org/t/just-a-little-help/28768/3 "2021-03-23T19:59:17Z")

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Hi,  
thank you so much for the reply,

but I’m not sure that particular problem is the reason for this not working.  
Because if I comment out the middle ‘else if’ statement it continues through the array as intended.

Something in the if-statement is causing it to not work past index 7 of the array but I don’t see what it could be.

(edited working version)  
[https://editor.p5js.org/cjstanleywinter/sketches/TKADWBYMT](https://editor.p5js.org/cjstanleywinter/sketches/TKADWBYMT)

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<div class="post-metadata">

**Author:** ![TfGuy44](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/tfguy44/32/41_2.png) [@TfGuy44](https://discourse.processing.org/u/TfGuy44)\
**Post date:** [March 23, 2021, 8:02pm UTC](https://discourse.processing.org/t/just-a-little-help/28768/4 "2021-03-23T20:02:18Z")

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```auto
* 7

* 8

* 9

Cannot read property 'sentences' of undefined (sketch: line 55)

* 10

```

Okay, fair. Maybe it can’t load a 10th narrative?

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<div class="post-metadata">

**Author:** ![cjswinter](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/cjswinter/32/12518_2.png) [@cjswinter](https://discourse.processing.org/u/cjswinter)\
**Post date:** [March 23, 2021, 8:03pm UTC](https://discourse.processing.org/t/just-a-little-help/28768/5 "2021-03-23T20:03:40Z")

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but uncomment that else-if statement and it won’t run past the 7th.  
I’m stumped

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<div class="post-metadata">

**Author:** ![josephh](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/josephh/32/210_2.png) [@josephh](https://discourse.processing.org/u/josephh)\
**Post date:** [March 25, 2021, 12:07am UTC](https://discourse.processing.org/t/just-a-little-help/28768/6 "2021-03-25T00:07:54Z")

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Hi @cjswinter ,

> [@cjswinter](#):
>
> but I’m not sure that particular problem is the reason for this not working.  
> Because if I comment out the middle ‘else if’ statement it continues through the array as intended.

Yes, with the code you provided this is exactly why it fails as explained by @TfGuy44 you are trying to access an element that is not in the array at location `10` (therefore returning `undefined` in JavaScript).

I tried to debug and understand your code but in my opinion, you shouldn’t mix `setTimeout` with p5js but rather use the `draw()` loop as a way to measure time and intervals and schedule your functions.

You are mixing a lot of async calls with timeout and it’s difficult to predict how the program flows.

Note that it doesn’t work past the 7th because it enters in the last `else` condition and you don’t use a `setTimeout` to redraw the ellipse… 😉