---
title: preSample
---
The `preSample` hook runs just before your pattern is sampled.
## Signature
```js
null hook(Pattern pattern)
```
## Example
```js
pattern.on('preSample', pattern => {
// Mutate the pattern object here
}
```
## Notes
The `preSample` hook is rarely used, but it's there if you need it.
It is triggered just before the start of either:
- the [Pattern.sampleOption()](/reference/api/pattern/sampleoption) method
- the [Pattern.sampleMeasurement()](/reference/api/pattern/samplemeasurement) method
- the [Pattern.sampleModels()](/reference/api/pattern/samplemodels) method
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