`string.casefold()`

Convert a String to lower case using a specified format.

Signature

casefold() => String

casefold(format: String) => String

Description

Converts the calling String to lower case. This method is similar to string.toLowerCase() but uses an optionally specified format. The calling String isn’t changed.

Parameters

Parameter Type Required Description

format

String

Unicode normalization form applied to the converted String:

Normalization form Description

NFKCCaseFold

(Default) Characters are decomposed by compatibility then recomposed by canonical equivalence.

NFC

Canonical decomposition followed by canonical composition. Characters are decomposed and then recomposed by canonical equivalence.

NFD

Canonical decomposition. Characters are decomposed by canonical equivalence, and multiple combining characters are arranged in order.

NFKC

Compatibility decomposition, followed by canonical composition. Characters are decomposed by compatibility then recomposed by canonical equivalence.

NFKD

Compatibility decomposition. Characters are decomposed by compatibility, and multiple combining characters are arranged in order.

Return value

Type	Description
String	Lower case version of the calling String.

Type

Description

String

Lower case version of the calling String.

Examples

Convert an email address to lower case using the default NFKC normalization form:
```
"john.doe@EXAMPLE.COM".casefold()
```
```
"john.doe@example.com"
```
Convert an email address to lower case using the NFC normalization form:
```
"john.doe@EXAMPLE.COM".casefold("NFC")
```
```
"john.doe@EXAMPLE.COM"
```
Default convert Unicode sequence to lower case:
```
"\uff21\u0030a\u0301".casefold()
```
```
"a0á"
```
Convert the same Unicode sequence using NFCK option:
```
"\uff21\u0030a\u0301".casefold("NFKC")
```
```
"A0á"
```
Convert the same Unicode sequence using NFC option:
```
"\uff21\u0030a\u0301".casefold("NFC")
```
```
"Ａ0á"
```