Convert strings to snake_case, camelCase, PascalCase, kebab-case and more! Supports Go initialisms, customization, and Unicode.
import "github.com/ettle/strcase"
Package strcase is a package for converting strings into various word cases (e.g. snake_case, camelCase)
go get -u github.com/ettle/strcase
Example usage
strcase.ToSnake("Hello World") // hello_world
strcase.ToSNAKE("Hello World") // HELLO_WORLD
strcase.ToKebab("helloWorld") // hello-world
strcase.ToKEBAB("helloWorld") // HELLO-WORLD
strcase.ToPascal("hello-world") // HelloWorld
strcase.ToCamel("hello-world") // helloWorld
// Handle odd cases
strcase.ToSnake("FOOBar") // foo_bar
// Support Go initialisms
strcase.ToGoPascal("http_response") // HTTPResponse
// Specify case and delimiter
strcase.ToCase("HelloWorld", strcase.UpperCase, '.') // HELLO.WORLD
String strcase is pretty straight forward and there are a number of methods to do it. This package is fully featured, more customizable, better tested, and faster than other packages and what you would probably whip up yourself.
We work for with unicode strings and pay very little performance penalty for it as we optimized for the common use case of ASCII only strings.
You can create a custom caser that changes the behavior to what you want. This customization also reduces the pressure for us to change the default behavior which means that things are more stable for everyone involved. The goal is to make the common path easy and fast, while making the uncommon path possible.
c := NewCaser(
// Use Go's default initialisms e.g. ID, HTML
true,
// Override initialisms (e.g. don't initialize HTML but initialize SSL
map[string]bool{"SSL": true, "HTML": false},
// Write your own custom SplitFn
//
NewSplitFn(
[]rune{'*', '.', ','},
SplitCase,
SplitAcronym,
PreserveNumberFormatting,
SplitBeforeNumber,
SplitAfterNumber,
))
assert.Equal(t, "http_200", c.ToSnake("http200"))
By default, we use the golint intialisms list. You can customize and override the initialisms if you wish to add additional ones, such as "SSL" or "CMS" or domain specific ones to your industry.
ToGoPascal("http_response") // HTTPResponse
ToGoSnake("http_response") // HTTP_response
We have a wide ranging test suite to make sure that we understand our behavior. Test coverage isn't everything, but we aim for 100% coverage.
Optimized to reduce memory allocations with Builder. Benchmarked and optimized around common cases.
We're on par with the fastest packages (that have less features) and much faster than others. We also benchmarked against code snippets. Using string builders to reduce memory allocation and reordering boolean checks for the common cases have a large performance impact.
Hopefully I was fair to each library and happy to rerun benchmarks differently or reword my commentary based on suggestions or updates.
// This package - faster then almost all libraries
// Initialisms are more complicated and slightly slower, but still fast
BenchmarkToTitle-96 9617142 125.7 ns/op 16 B/op 1 allocs/op
BenchmarkToSnake-96 10659919 120.7 ns/op 16 B/op 1 allocs/op
BenchmarkToSNAKE-96 9018282 126.4 ns/op 16 B/op 1 allocs/op
BenchmarkToGoSnake-96 4903687 254.5 ns/op 26 B/op 4 allocs/op
BenchmarkToCustomCaser-96 4434489 265.0 ns/op 28 B/op 4 allocs/op
// Segment has very fast snake case and camel case libraries
// No features or customization, but very very fast
BenchmarkSegment-96 33625734 35.54 ns/op 16 B/op 1 allocs/op
// Iancoleman has gotten some performance improvements, but remains
// without unicode support and lacks fine-grained customization
BenchmarkToSnakeIan-96 13141522 92.99 ns/op 16 B/op 1 allocs/op
// Stdlib strings.Title is deprecated; using golang.org/x.text
BenchmarkGolangOrgXTextCases-96 4665676 262.5 ns/op 272 B/op 2 allocs/op
// Other libraries or code snippets
// - Most are slower, by up to an order of magnitude
// - No support for initialisms or customization
// - Some generate only camelCase or snake_case
// - Many lack unicode support
BenchmarkToSnakeStoewer-96 8095468 148.9 ns/op 64 B/op 2 allocs/op
// Copying small rune arrays is slow
BenchmarkToSnakeSiongui-96 2912593 401.7 ns/op 112 B/op 19 allocs/op
BenchmarkGoValidator-96 3493800 342.6 ns/op 184 B/op 9 allocs/op
// String alloction is slow
BenchmarkToSnakeFatih-96 1282648 945.1 ns/op 616 B/op 26 allocs/op
// Regexp is slow
BenchmarkToSnakeGolangPrograms-96 778674 1495 ns/op 227 B/op 11 allocs/op
// These results aren't a surprise - my initial version of this library was
// painfully slow. I think most of us, without spending some time with
// profilers and benchmarks, would write also something on the slower side.
That's right - zero. We only import the Go standard library. No hassles with dependencies, licensing, security alerts.
If every nanosecond matters and this is used in a tight loop, use segment.io's libraries (https://github.com/segmentio/go-snakecase and https://github.com/segmentio/go-camelcase). They lack features, but make up for it by being blazing fast.
If you are migrating from from another package, you may find slight differences in output. To reduce the delta, you may find it helpful to use the following custom casers to mimic the behavior of the other package.
// From <a href="https://github.com/iancoleman/strcase">https://github.com/iancoleman/strcase</a>
var c = NewCaser(false, nil, NewSplitFn([]rune{'_', '-', '.'}, SplitCase, SplitAcronym, SplitBeforeNumber))
// From <a href="https://github.com/stoewer/go-strcase">https://github.com/stoewer/go-strcase</a>
var c = NewCaser(false, nil, NewSplitFn([]rune{'_', '-'}, SplitCase), SplitAcronym)
- func ToCamel(s string) string
- func ToCase(s string, wordCase WordCase, delimiter rune) string
- func ToGoCamel(s string) string
- func ToGoCase(s string, wordCase WordCase, delimiter rune) string
- func ToGoKebab(s string) string
- func ToGoPascal(s string) string
- func ToGoSnake(s string) string
- func ToKEBAB(s string) string
- func ToKebab(s string) string
- func ToPascal(s string) string
- func ToSNAKE(s string) string
- func ToSnake(s string) string
- type Caser
- func NewCaser(goInitialisms bool, initialismOverrides map[string]bool, splitFn SplitFn) *Caser
- func (c *Caser) ToCamel(s string) string
- func (c *Caser) ToCase(s string, wordCase WordCase, delimiter rune) string
- func (c *Caser) ToKEBAB(s string) string
- func (c *Caser) ToKebab(s string) string
- func (c *Caser) ToPascal(s string) string
- func (c *Caser) ToSNAKE(s string) string
- func (c *Caser) ToSnake(s string) string
- type SplitAction
- type SplitFn
- type SplitOption
- type WordCase
func ToCamel(s string) stringToCamel returns words in camelCase (capitalized words concatenated together, with first word lower case). Also known as lowerCamelCase or mixedCase.
func ToCase(s string, wordCase WordCase, delimiter rune) stringToCase returns words in given case and delimiter.
func ToGoCamel(s string) stringToGoCamel returns words in camelCase (capitalized words concatenated together, with first word lower case). Also known as lowerCamelCase or mixedCase.
Respects Go's common initialisms, but first word remains lowercased which is important for code generator use cases (e.g. toJson -> toJSON, httpResponse -> httpResponse).
func ToGoCase(s string, wordCase WordCase, delimiter rune) stringToGoCase returns words in given case and delimiter.
Respects Go's common initialisms (e.g. httpResponse -> HTTPResponse).
func ToGoKebab(s string) stringToGoKebab returns words in kebab-case (lower case words with dashes). Also known as dash-case.
Respects Go's common initialisms (e.g. http-response -> HTTP-response).
func ToGoPascal(s string) stringToGoPascal returns words in PascalCase (capitalized words concatenated together). Also known as UpperPascalCase.
Respects Go's common initialisms (e.g. HttpResponse -> HTTPResponse).
func ToGoSnake(s string) stringToGoSnake returns words in snake_case (lower case words with underscores).
Respects Go's common initialisms (e.g. http_response -> HTTP_response).
func ToKEBAB(s string) stringToKEBAB returns words in KEBAB-CASE (upper case words with dashes). Also known as SCREAMING-KEBAB-CASE or SCREAMING-DASH-CASE.
func ToKebab(s string) stringToKebab returns words in kebab-case (lower case words with dashes). Also known as dash-case.
func ToPascal(s string) stringToPascal returns words in PascalCase (capitalized words concatenated together). Also known as UpperPascalCase.
func ToSNAKE(s string) stringToSNAKE returns words in SNAKE_CASE (upper case words with underscores). Also known as SCREAMING_SNAKE_CASE or UPPER_CASE.
func ToSnake(s string) stringToSnake returns words in snake_case (lower case words with underscores).
type Caser struct {
// contains filtered or unexported fields
}Caser allows for customization of parsing and intialisms
func NewCaser(goInitialisms bool, initialismOverrides map[string]bool, splitFn SplitFn) *CaserNewCaser returns a configured Caser.
A Caser should be created when you want fine grained control over how the words are split.
Notes on function arguments
goInitialisms: Whether to use Golint's intialisms
initialismOverrides: A mapping of extra initialisms
Keys must be in ALL CAPS. Merged with Golint's if goInitialisms is set.
Setting a key to false will override Golint's.
splitFn: How to separate words
Override the default split function. Consider using NewSplitFn to
configure one instead of writing your own.
func (c *Caser) ToCamel(s string) stringToCamel returns words in camelCase (capitalized words concatenated together, with first word lower case). Also known as lowerCamelCase or mixedCase.
func (c *Caser) ToCase(s string, wordCase WordCase, delimiter rune) stringToCase returns words with a given case and delimiter.
func (c *Caser) ToKEBAB(s string) stringToKEBAB returns words in KEBAB-CASE (upper case words with dashes). Also known as SCREAMING-KEBAB-CASE or SCREAMING-DASH-CASE.
func (c *Caser) ToKebab(s string) stringToKebab returns words in kebab-case (lower case words with dashes). Also known as dash-case.
func (c *Caser) ToPascal(s string) stringToPascal returns words in PascalCase (capitalized words concatenated together). Also known as UpperPascalCase.
func (c *Caser) ToSNAKE(s string) stringToSNAKE returns words in SNAKE_CASE (upper case words with underscores). Also known as SCREAMING_SNAKE_CASE or UPPER_CASE.
func (c *Caser) ToSnake(s string) stringToSnake returns words in snake_case (lower case words with underscores).
type SplitAction intSplitAction defines if and how to split a string
const (
// Noop - Continue to next character
Noop SplitAction = iota
// Split - Split between words
// e.g. to split between wordsWithoutDelimiters
Split
// SkipSplit - Split the word and drop the character
// e.g. to split words with delimiters
SkipSplit
// Skip - Remove the character completely
Skip
)type SplitFn func(prev, curr, next rune) SplitActionSplitFn defines how to split a string into words
func NewSplitFn(
delimiters []rune,
splitOptions ...SplitOption,
) SplitFnNewSplitFn returns a SplitFn based on the options provided.
NewSplitFn covers the majority of common options that other strcase libraries provide and should allow you to simply create a custom caser. For more complicated use cases, feel free to write your own SplitFn
type SplitOption intSplitOption are options that allow for configuring NewSplitFn
const (
// SplitCase - FooBar -> Foo_Bar
SplitCase SplitOption = iota
// SplitAcronym - FOOBar -> Foo_Bar
// It won't preserve FOO's case. If you want, you can set the Caser's initialisms so FOO will be in all caps
SplitAcronym
// SplitBeforeNumber - port80 -> port_80
SplitBeforeNumber
// SplitAfterNumber - 200status -> 200_status
SplitAfterNumber
// PreserveNumberFormatting - a.b.2,000.3.c -> a_b_2,000.3_c
PreserveNumberFormatting
)type WordCase intWordCase is an enumeration of the ways to format a word.
const (
// Original - Preserve the original input strcase
Original WordCase = iota
// LowerCase - All letters lower cased (example)
LowerCase
// UpperCase - All letters upper cased (EXAMPLE)
UpperCase
// TitleCase - Only first letter upper cased (Example)
TitleCase
// CamelCase - TitleCase except lower case first word (exampleText)
// Notably, even if the first word is an initialism, it will be lower
// cased. This is important for code generators where capital letters
// mean exported functions. i.e. jsonString(), not JSONString()
CamelCase
)