Go Strcase

Convert strings to snake_case, camelCase, PascalCase, kebab-case and more! Supports Go initialisms, customization, and Unicode.

import "github.com/ettle/strcase"

<a name="pkg-overview">Overview</a>

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

Why this package

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.

Unicode support

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.

Customization

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"))

Initialism support

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

Test coverage

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.

Fast

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.

Zero dependencies

That's right - zero. We only import the Go standard library. No hassles with dependencies, licensing, security alerts.

Why not this package

If every nanosecond matters and this is used in a tight loop, use segment.io's libraries (<a href="https://github.com/segmentio/go-snakecase">https://github.com/segmentio/go-snakecase</a> and <a href="https://github.com/segmentio/go-camelcase">https://github.com/segmentio/go-camelcase</a>). They lack features, but make up for it by being blazing fast.

Migrating from other packages

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)

<a name="pkg-index">Index</a>

• 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
  • func NewSplitFn(delimiters []rune, splitOptions ...SplitOption) SplitFn
• type SplitOption
• type WordCase

<a name="ToCamel">func</a> ToCamel

func ToCamel(s string) string

ToCamel returns words in camelCase (capitalized words concatenated together, with first word lower case). Also known as lowerCamelCase or mixedCase.

<a name="ToCase">func</a> ToCase

func ToCase(s string, wordCase WordCase, delimiter rune) string

ToCase returns words in given case and delimiter.

<a name="ToGoCamel">func</a> ToGoCamel

func ToGoCamel(s string) string

ToGoCamel 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).

<a name="ToGoCase">func</a> ToGoCase

func ToGoCase(s string, wordCase WordCase, delimiter rune) string

ToGoCase returns words in given case and delimiter.

Respects Go's common initialisms (e.g. httpResponse -> HTTPResponse).

<a name="ToGoKebab">func</a> ToGoKebab

func ToGoKebab(s string) st