---
title: strings.isUpper() function
description: strings.isUpper() tests if a single character string is uppercase.
url: https://docs.influxdata.com/flux/v0/stdlib/strings/isupper/
estimated_tokens: 582
product: Flux
version: v0
publisher: InfluxData
canonical: https://docs.influxdata.com/flux/v0/stdlib/strings/isupper/
date: '2024-04-08T16:01:02-06:00'
lastmod: '2024-04-08T16:01:02-06:00'
---

* Flux 0.18.0+

InfluxDB support

`strings.isUpper()` tests if a single character string is uppercase.

##### Function type signature

```js
(v: string) => bool
```

For more information, see [Function type signatures](/flux/v0/function-type-signatures/).

## Parameters

### v

(Required)
Single-character string value to test.

## Examples

### Filter by columns with single-letter uppercase values

```js
import "strings"

data
    |> filter(fn: (r) => strings.isUpper(v: r._value))
```

[](#view-example-input-and-output)

View example input and output

#### Input data

|       \_time       |\*tag|\_value|
|--------------------|-----|-------|
|2022-01-01T00:00:00Z| t1  |   a   |
|2022-01-01T00:01:00Z| t1  |   B   |
|2022-01-01T00:02:00Z| t1  |   C   |
|2022-01-01T00:03:00Z| t1  |   d   |
|2022-01-01T00:04:00Z| t1  |   e   |

|       \_time       |\*tag|\_value|
|--------------------|-----|-------|
|2022-01-01T00:00:00Z| t2  |   F   |
|2022-01-01T00:01:00Z| t2  |   g   |
|2022-01-01T00:02:00Z| t2  |   H   |
|2022-01-01T00:03:00Z| t2  |   i   |
|2022-01-01T00:04:00Z| t2  |   J   |

#### Output data

|       \_time       |\*tag|\_value|
|--------------------|-----|-------|
|2022-01-01T00:01:00Z| t1  |   B   |
|2022-01-01T00:02:00Z| t1  |   C   |

|       \_time       |\*tag|\_value|
|--------------------|-----|-------|
|2022-01-01T00:00:00Z| t2  |   F   |
|2022-01-01T00:02:00Z| t2  |   H   |
|2022-01-01T00:04:00Z| t2  |   J   |

#### Related

* [strings.isLower() function](/flux/v0/stdlib/strings/islower/)
| _time | *tag | _value |
| --- | --- | --- |
| _time | *tag | _value |
| 2022-01-01T00:00:00Z | t1 | a |
| 2022-01-01T00:01:00Z | t1 | B |
| 2022-01-01T00:02:00Z | t1 | C |
| 2022-01-01T00:03:00Z | t1 | d |
| 2022-01-01T00:04:00Z | t1 | e |

| _time | *tag | _value |
| --- | --- | --- |
| _time | *tag | _value |
| 2022-01-01T00:00:00Z | t2 | F |
| 2022-01-01T00:01:00Z | t2 | g |
| 2022-01-01T00:02:00Z | t2 | H |
| 2022-01-01T00:03:00Z | t2 | i |
| 2022-01-01T00:04:00Z | t2 | J |

| _time | *tag | _value |
| --- | --- | --- |
| _time | *tag | _value |
| 2022-01-01T00:01:00Z | t1 | B |
| 2022-01-01T00:02:00Z | t1 | C |

| _time | *tag | _value |
| --- | --- | --- |
| _time | *tag | _value |
| 2022-01-01T00:00:00Z | t2 | F |
| 2022-01-01T00:02:00Z | t2 | H |
| 2022-01-01T00:04:00Z | t2 | J |