docs-v2/content/flux/v0/stdlib/universe/contains.md

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---
title: contains() function
description: >
`contains()` tests if an array contains a specified value and returns `true` or `false`.
menu:
flux_v0_ref:
name: contains
parent: universe
identifier: universe/contains
weight: 101
introduced: 0.19.0
---
<!------------------------------------------------------------------------------
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function definition in the Flux source code:
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`contains()` tests if an array contains a specified value and returns `true` or `false`.
##### Function type signature
```js
(set: [A], value: A) => bool where A: Nullable
```
{{% caption %}}
For more information, see [Function type signatures](/flux/v0/function-type-signatures/).
{{% /caption %}}
## Parameters
### value
({{< req >}})
Value to search for.
### set
({{< req >}})
Array to search.
## Examples
### Filter on a set of specific fields
```js
fields = ["f1", "f2"]
data
|> filter(fn: (r) => contains(value: r._field, set: fields))
```
{{< expand-wrapper >}}
{{% expand "View example input and output" %}}
#### Input data
| _time | _value | *tag | *_field | _measurement |
| -------------------- | ------- | ---- | ------- | ------------- |
| 2021-01-01T00:00:00Z | -2 | t1 | f1 | m |
| 2021-01-01T00:00:50Z | 4 | t1 | f1 | m |
| _time | _value | *tag | _measurement | *_field |
| ------ | ------- | ---- | ------------- | ------- |
| _time | _value | *tag | _measurement | *_field |
| -------------------- | ------- | ---- | ------------- | ------- |
| 2021-01-01T00:00:10Z | 4 | t2 | m | f1 |
| 2021-01-01T00:00:20Z | -3 | t2 | m | f1 |
| 2021-01-01T00:00:50Z | 1 | t2 | m | f1 |
| _time | _value | *tag | *_field | _measurement |
| ------ | ------- | ---- | ------- | ------------- |
| _time | _value | *tag | *_field | _measurement |
| -------------------- | ------- | ---- | ------- | ------------- |
| 2021-01-01T00:00:10Z | 10 | t1 | f2 | m |
| 2021-01-01T00:00:20Z | 7 | t1 | f2 | m |
| _time | _value | *tag | *_field | _measurement |
| -------------------- | ------- | ---- | ------- | ------------- |
| 2021-01-01T00:00:30Z | 17 | t1 | f3 | m |
| 2021-01-01T00:00:40Z | 15 | t1 | f3 | m |
| _time | _value | *tag | _measurement | *_field |
| ------ | ------- | ---- | ------------- | ------- |
| _time | _value | *tag | _measurement | *_field |
| -------------------- | ------- | ---- | ------------- | ------- |
| 2021-01-01T00:00:00Z | 19 | t2 | m | f3 |
| 2021-01-01T00:00:30Z | 19 | t2 | m | f3 |
| 2021-01-01T00:00:40Z | 13 | t2 | m | f3 |
#### Output data
| _time | _value | *tag | *_field | _measurement |
| -------------------- | ------- | ---- | ------- | ------------- |
| 2021-01-01T00:00:00Z | -2 | t1 | f1 | m |
| 2021-01-01T00:00:50Z | 4 | t1 | f1 | m |
| _time | _value | *tag | _measurement | *_field |
| ------ | ------- | ---- | ------------- | ------- |
| _time | _value | *tag | _measurement | *_field |
| -------------------- | ------- | ---- | ------------- | ------- |
| 2021-01-01T00:00:10Z | 4 | t2 | m | f1 |
| 2021-01-01T00:00:20Z | -3 | t2 | m | f1 |
| 2021-01-01T00:00:50Z | 1 | t2 | m | f1 |
| _time | _value | *tag | *_field | _measurement |
| ------ | ------- | ---- | ------- | ------------- |
| _time | _value | *tag | *_field | _measurement |
| -------------------- | ------- | ---- | ------- | ------------- |
| 2021-01-01T00:00:10Z | 10 | t1 | f2 | m |
| 2021-01-01T00:00:20Z | 7 | t1 | f2 | m |
{{% /expand %}}
{{< /expand-wrapper >}}