45 lines
944 B
Markdown
45 lines
944 B
Markdown
---
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title: strings.isLetter() function
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description: The strings.isLetter() function tests if a single character string is a letter (a-z, A-Z).
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aliases:
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- /influxdb/v2.0/reference/flux/functions/strings/isletter/
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- /influxdb/v2.0/reference/flux/stdlib/strings/isletter/
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- /influxdb/cloud/reference/flux/stdlib/strings/isletter/
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menu:
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flux_0_x_ref:
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name: strings.isLetter
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parent: strings
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weight: 301
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flux/v0.x/tags: [tests]
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related:
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- /flux/v0.x/stdlib/strings/isdigit/
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introduced: 0.18.0
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---
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The `strings.isLetter()` function tests if a single character string is a letter (a-z, A-Z).
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_**Output data type:** Boolean_
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```js
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import "strings"
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strings.isLetter(v: "A")
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// returns true
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```
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## Parameters
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### v {data-type="string"}
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The single character string to test.
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## Examples
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###### Filter by columns with single-letter values
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```js
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import "strings"
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data
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|> filter(fn: (r) => strings.isLetter(v: r.serverRef))
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```
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