---
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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`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 >}}