@rbxts/jsnatives

toUpperCase

Converts a string to uppercase.

Signature

function toUpperCase(str: string): string

Description

The toUpperCase function converts all the alphabetic characters in a string to uppercase. It uses Lua's string.upper function internally.

Parameters

str: The string to convert to uppercase.

Return value

A new string with all alphabetic characters converted to uppercase.

Examples

Basic usage

// Convert a string to uppercase
const upper = String.toUpperCase("hello world");
print(upper); // Outputs: "HELLO WORLD"

// Mixed case conversion
const mixed = String.toUpperCase("Hello World");
print(mixed); // Outputs: "HELLO WORLD"

Case preservation for non-alphabetic characters

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

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

Handling edge cases

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

// Already uppercase
const alreadyUpper = String.toUpperCase("HELLO WORLD");
print(alreadyUpper); // Outputs: "HELLO WORLD"

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

Practical applications

// Create headings or emphasis
function createHeading(text: string): string {
  return String.toUpperCase(text);
}

print(createHeading("important notice")); // Outputs: "IMPORTANT NOTICE"

// Format constants
function formatConstantName(name: string): string {
  return String.toUpperCase(String.replace(name, " ", "_"));
}

print(formatConstantName("max items")); // Outputs: "MAX_ITEMS"

Using with other string functions

// Combine with other string functions for more complex operations
function emphasizeFirstWord(text: string): string {
  const words = String.split(text, " ");
  if (words.length > 0) {
    words[0] = String.toUpperCase(words[0]);
  }
  return words.join(" ");
}

print(emphasizeFirstWord("welcome to our website")); // Outputs: "WELCOME to our website"

// Create acronyms
function createAcronym(phrase: string): string {
  const words = String.split(phrase, " ");
  let acronym = "";

  for (const word of words) {
    if (word.length > 0) {
      acronym += String.toUpperCase(word[0]);
    }
  }

  return acronym;
}

print(createAcronym("as soon as possible")); // Outputs: "ASAP"
print(createAcronym("national aeronautics and space administration")); // Outputs: "NAASA"

Comparison with toLowerCase

// Original string
const original = "Hello World 123";

// Convert to uppercase
const upper = String.toUpperCase(original);
print(upper); // Outputs: "HELLO WORLD 123"

// Convert to lowercase
const lower = String.toLowerCase(original);
print(lower); // Outputs: "hello world 123"

// Converting between cases
print(String.toLowerCase(upper)); // Outputs: "hello world 123"
print(String.toUpperCase(lower)); // Outputs: "HELLO WORLD 123"