# e.findIdx is not a function

**URL:** https://forum.makecode.com/t/e-findidx-is-not-a-function/8016
**Category:** Help
**Created:** [May 11, 2021, 6:55pm UTC](https://forum.makecode.com/t/e-findidx-is-not-a-function/8016 "2021-05-11T18:55:23Z")
**Posts on this page:** 2
**Page:** 1

<div class="post-metadata">

### Author: ![awful-coder](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.makecode.com/awful-coder/32/3760_2.png) [@awful-coder](https://forum.makecode.com/u/awful-coder)
#### Post date: [May 11, 2021, 6:55pm UTC](https://forum.makecode.com/t/e-findidx-is-not-a-function/8016/1 "2021-05-11T18:55:23Z")

</div>

hey uh is there any known things that can cause the following error message?

```
Simulator crashed, no error handler TypeError: e.findIdx is not a function
at Object.s (https://pxt.azureedge.net/blob/4b21e7286becc7c46be95397d4a314bccec49b31/pxtsim.js:1:49755)
```

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<div class="post-metadata">

### Author: ![awful-coder](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.makecode.com/awful-coder/32/3760_2.png) [@awful-coder](https://forum.makecode.com/u/awful-coder)
#### Post date: [May 11, 2021, 9:57pm UTC](https://forum.makecode.com/t/e-findidx-is-not-a-function/8016/2 "2021-05-11T21:57:53Z")

</div>

ok so i actually fixed it  
so i had an array  
let arr:[number,number][];  
…  
let x = arr[0];

and when i try to access  
x[i]

it throws the error

but if i declare x as number[] then it doesnt happen