大小写转换器

// camelCase → snake_case
function toSnakeCase(str) {
  return str
    .replace(/([a-z])([A-Z])/g, '$1_$2')
    .replace(/[\s-]+/g, '_')
    .toLowerCase()
}
toSnakeCase('myVariableName')  // → "my_variable_name"
toSnakeCase('kebab-case-str')  // → "kebab_case_str"

// snake_case → camelCase
function toCamelCase(str) {
  return str
    .toLowerCase()
    .replace(/[_-](\w)/g, (_, c) => c.toUpperCase())
}
toCamelCase('my_variable_name')  // → "myVariableName"

// Title Case
function toTitleCase(str) {
  return str.replace(/\w\S*/g, w =>
    w.charAt(0).toUpperCase() + w.slice(1).toLowerCase()
  )
}
toTitleCase('the quick brown fox')  // → "The Quick Brown Fox"

import re

text = "the quick brown fox"

# UPPERCASE / lowercase
text.upper()  # → "THE QUICK BROWN FOX"
text.lower()  # → "the quick brown fox"

# Title Case
text.title()  # → "The Quick Brown Fox"

# camelCase
def to_camel(s):
    words = re.split(r'[\s_-]+', s)
    return words[0].lower() + ''.join(w.capitalize() for w in words[1:])

to_camel("my_variable_name")  # → "myVariableName"

# snake_case from camelCase
def to_snake(s):
    return re.sub(r'([a-z])([A-Z])', r'\1_\2', s).lower()

to_snake("myVariableName")  # → "my_variable_name"

# kebab-case
def to_kebab(s):
    return re.sub(r'([a-z])([A-Z])', r'\1-\2', s).replace('_', '-').lower()

to_kebab("myVariableName")  # → "my-variable-name"

package main

import (
	"fmt"
	"regexp"
	"strings"
)

// camelCase → snake_case
func toSnake(s string) string {
	re := regexp.MustCompile("([a-z])([A-Z])")
	snake := re.ReplaceAllString(s, "${1}_${2}")
	return strings.ToLower(snake)
}

// snake_case → camelCase
func toCamel(s string) string {
	parts := strings.Split(strings.ToLower(s), "_")
	for i := 1; i < len(parts); i++ {
		parts[i] = strings.Title(parts[i])
	}
	return strings.Join(parts, "")
}

func main() {
	fmt.Println(toSnake("myVariableName"))  // → my_variable_name
	fmt.Println(toCamel("my_variable_name")) // → myVariableName
	fmt.Println(strings.ToUpper("hello"))    // → HELLO
	fmt.Println(strings.ToUpper("hello world")) // → HELLO WORLD
}

# UPPERCASE
echo "hello world" | tr '[:lower:]' '[:upper:]'
# → HELLO WORLD

# lowercase
echo "HELLO WORLD" | tr '[:upper:]' '[:lower:]'
# → hello world

# camelCase → snake_case (using sed)
echo "myVariableName" | sed 's/\([a-z]\)\([A-Z]\)/\1_\2/g' | tr '[:upper:]' '[:lower:]'
# → my_variable_name

# snake_case → kebab-case
echo "my_variable_name" | tr '_' '-'
# → my-variable-name