@rbxts/jsnatives

toLowerCase

Converts a string to lowercase.

Signature

function toLowerCase(str: string): string

Description

The toLowerCase function converts all the alphabetic characters in a string to lowercase. It uses Lua's string.lower function internally.

Parameters

str: The string to convert to lowercase.

Return value

A new string with all alphabetic characters converted to lowercase.

Examples

Basic usage

// Convert a string to lowercase
const lower = String.toLowerCase("HELLO WORLD");
print(lower); // Outputs: "hello world"

// Mixed case conversion
const mixed = String.toLowerCase("Hello World");
print(mixed); // Outputs: "hello world"

Case preservation for non-alphabetic characters

// Numbers and special characters are not affected
const withNumbers = String.toLowerCase("HELLO 123!");
print(withNumbers); // Outputs: "hello 123!"

// Only alphabetic characters are converted
const special = String.toLowerCase("ABC-DEF_GHI@JKL");
print(special); // Outputs: "abc-def_ghi@jkl"

Handling edge cases

// Empty string
const empty = String.toLowerCase("");
print(empty); // Outputs: ""

// Already lowercase
const alreadyLower = String.toLowerCase("hello world");
print(alreadyLower); // Outputs: "hello world"

// Non-alphabetic characters
const nonAlpha = String.toLowerCase("123!@#");
print(nonAlpha); // Outputs: "123!@#" (unchanged)

Practical applications

// Case-insensitive comparison
function compareIgnoreCase(str1: string, str2: string): boolean {
  return String.toLowerCase(str1) === String.toLowerCase(str2);
}

print(compareIgnoreCase("Hello", "hello")); // Outputs: true
print(compareIgnoreCase("World", "earth")); // Outputs: false

// Normalizing user input
function normalizeInput(input: string): string {
  return String.toLowerCase(input);
}

print(normalizeInput("John.Doe@Example.COM")); // Outputs: "john.doe@example.com"

Using with other string functions

// Combine with other string functions for more complex operations
function isYesResponse(response: string): boolean {
  const normalized = String.toLowerCase(String.trim(response));
  return normalized === "yes" || normalized === "y";
}

print(isYesResponse("  YES  ")); // Outputs: true
print(isYesResponse("y")); // Outputs: true
print(isYesResponse("No")); // Outputs: false

// Case-insensitive search
function containsIgnoreCase(text: string, search: string): boolean {
  return String.includes(String.toLowerCase(text), String.toLowerCase(search));
}

print(containsIgnoreCase("Hello World", "world")); // Outputs: true
print(containsIgnoreCase("JavaScript", "SCRIPT")); // Outputs: true