snakeCase()

snakeCase(str): string

Converts a string to snake_case.

remarque

Handles camelCase, PascalCase, acronyms, kebab-case, and spaces.

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Parameters

str: string

The string to convert.

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Returns: string

The string in snake_case.

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Since

2.0.0

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Performance

O(n) where n is string length. Single regex pass with match + join.

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Also known as

snake (Radashi) · snakeCase (Lodash, es-toolkit, Modern Dash) · toSnakeCase (Remeda) · ❌ (Ramda, Effect, Antfu)

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Example

snakeCase('helloWorld');     // => 'hello_world'
snakeCase('XMLHttpRequest'); // => 'xml_http_request'
snakeCase('hello-world');    // => 'hello_world'
snakeCase('Hello World');    // => 'hello_world'
snakeCase('--foo--bar--');   // => 'foo_bar'

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How it works?

Converts a string to snake_case format. All lowercase, words separated by underscores.

Conversion Examples

Input	Output
helloWorld	hello_world
XMLHttpRequest	xml_http_request
hello-world	hello_world
Hello World	hello_world

Process

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Use Cases

Format database columns 📌

Convert strings to snake_case for database column names or Python API compatibility. Critical for backend integration.

#format#database#columns#snake_case#Python#backend

const column = snakeCase('userId'); // 'user_id'

Convert payload keys before sending to a Python/Ruby API

Transform camelCase JavaScript keys into snake_case before sending to a backend API. The reverse of the camelCase normalization — essential for full-stack interop.

#convert#payload#keys#camelCase#snake_case#API#Python#Ruby#backend

const payload = {
  userId: 42,
  firstName: "Alice",
  isActive: true,
};

// Combined with mapKeys for full object transformation
const apiPayload = mapKeys(payload, (_, key) => snakeCase(key));
// => { user_id: 42, first_name: "Alice", is_active: true }

await fetch("/api/users", {
  method: "POST",
  body: JSON.stringify(apiPayload),
});