# Does the "function" node have a bug?

**URL:** <https://discourse.nodered.org/t/does-the-function-node-have-a-bug/82146>\
**Category:** General\
**Tags:** function-node, pdf\
**Created:** [18 October 2023 07:33 UTC](https://discourse.nodered.org/t/does-the-function-node-have-a-bug/82146 "2023-10-18T07:33:44Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![jase](https://avatars.discourse-cdn.com/v4/letter/j/dbc845/32.png) [@jase](https://discourse.nodered.org/u/jase)\
**Post date:** [18 October 2023 07:33 UTC](https://discourse.nodered.org/t/does-the-function-node-have-a-bug/82146/1 "2023-10-18T07:33:44Z")

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Hi Community,

I currently try to use Nodered to process PDF files. So I tried I'm testing a very simple flow like "reading a local PDF file" and then "extracting text" with a function.

The object returned by the PDF node is an array with the first level being the pages (in my case page 0 and page 1) and the second one containing the text elements with 4 features. In my use case, I try to retrieve the text ie "t" element.

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/a/b/aba8a14c5b6545ad587953d3c678dcb878769f5e.png)

Then using the function node, I noticed a strange behaviour in my function code.

When I use """let eli = pdf[i].t""" the node works fine and returns the payload. But when I use (and I need it for further computation) """let eli = pdf[i+1].t""" it returns a "TypeError"

I tried to declare "i" at the beginning of the code, but nothing changes.  
Am I missing something?

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**Author:** ![kuema](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/kuema/32/6542_2.png) [@kuema](https://discourse.nodered.org/u/kuema)\
**Post date:** [18 October 2023 07:44 UTC](https://discourse.nodered.org/t/does-the-function-node-have-a-bug/82146/2 "2023-10-18T07:44:17Z")

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Looks like an "off-by-one" error to me.

The last iteration won't work, because you access an index larger than the array's length. The last iteration of `pdf[i+1]` yields `undefined`, hence the type error.

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**Author:** ![hotNipi](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/hotnipi/32/383_2.png) [@hotNipi](https://discourse.nodered.org/u/hotNipi)\
**Post date:** [18 October 2023 07:56 UTC](https://discourse.nodered.org/t/does-the-function-node-have-a-bug/82146/3 "2023-10-18T07:56:08Z")

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@kuema is right.

Here's a playground for you to practice the iteration

```auto
let pdf = [{ name: 'first', t: 0 }, { name: 'second', t: 1 }, { name: 'third', t: 2 }]
let len = pdf.length
node.warn(pdf)
node.warn(len)

for(let i = 0;i<=len-1;i++){
    node.warn('a) i: ' + i + ' | pdf[i+1]: ' + pdf[i+1])
}
// i<=len-1
// is same as
// i < len
// so you can remove that overcomplication

for (let i = 0; i < len; i++) {
    node.warn('b) i: ' + i + ' | pdf[i+1]: ' + pdf[i + 1])
}

// But your problem is that in case of i==2 the pdf[i+1] 
// tries to reach an element from outside
// of array boundaries. (pdf[3] desn't exist) The result is undefined
// You can't ask any property (pdf[3].t) of undefined

//this will now fail
for (let i = 0; i < len; i++) {
    node.warn('b) i: ' + i + ' | pdf[i+1].t: ' + pdf[i + 1].t)
}

```

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<div class="post-metadata">

**Author:** ![jase](https://avatars.discourse-cdn.com/v4/letter/j/dbc845/32.png) [@jase](https://discourse.nodered.org/u/jase)\
**Post date:** [18 October 2023 09:25 UTC](https://discourse.nodered.org/t/does-the-function-node-have-a-bug/82146/4 "2023-10-18T09:25:00Z")

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Hi @kuema, @hotNipi,

You're right. Reading now your responses, it appears quite obvious. I confused length and boundary index. By limiting the loop to "i\<=len-2" (or "i\<len-1") it works. I got to be more watchful.

Anyway thanks a lot to you, I thought I was stuck here.  
Cheers,  
Jase

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [1 November 2023 09:25 UTC](https://discourse.nodered.org/t/does-the-function-node-have-a-bug/82146/5 "2023-11-01T09:25:59Z")

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