---
title: strings.isLower() function
description: strings.isLower() tests if a single-character string is lowercase.
url: https://docs.influxdata.com/flux/v0/stdlib/strings/islower/
estimated_tokens: 978
product: Flux
version: v0
---

# strings.isLower() function

-   Flux 0.18.0+
-   View InfluxDB support

`strings.isLower()` tests if a single-character string is lowercase.

##### 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 lowercase values

```js
import "strings"

data
    |> filter(fn: (r) => strings.isLower(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 |
| --- | --- | --- |
| 2022-01-01T00:00:00Z | t1 | a |
| 2022-01-01T00:03:00Z | t1 | d |
| 2022-01-01T00:04:00Z | t1 | e |

| _time | *tag | _value |
| --- | --- | --- |
| 2022-01-01T00:01:00Z | t2 | g |
| 2022-01-01T00:03:00Z | t2 | i |

#### Related

-   [strings.isUpper() function](/flux/v0/stdlib/strings/isupper/)