fix(text): use locale-independent letter case methods (#6016)

text/_util.ts

@@ -16,7 +16,5 @@ export function splitToWords(input: string) {
 }
 
 export function capitalizeWord(word: string): string {
-  return word
-    ? word?.[0]?.toLocaleUpperCase() + word.slice(1).toLocaleLowerCase()
-    : word;
+  return word ? word[0]!.toUpperCase() + word.slice(1).toLowerCase() : word;
 }

text/_util_test.ts

@@ -1,7 +1,7 @@
 // Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
 
 import { assertEquals } from "@std/assert";
-import { splitToWords } from "./_util.ts";
+import { capitalizeWord, splitToWords } from "./_util.ts";
 
 Deno.test({
   name: "split() returns an empty array for an empty string",
@@ -155,3 +155,45 @@ Deno.test({
     assertEquals(result, expected);
   },
 });
+
+Deno.test({
+  name: "capitalizeWord() handles empty string",
+  fn() {
+    assertEquals(capitalizeWord(""), "");
+  },
+});
+
+Deno.test({
+  name: "capitalizeWord() handles single char",
+  fn() {
+    assertEquals(capitalizeWord("a"), "A");
+  },
+});
+
+Deno.test({
+  name: "capitalizeWord() handles multiple chars",
+  fn() {
+    assertEquals(capitalizeWord("aa"), "Aa");
+  },
+});
+
+Deno.test({
+  name: "capitalizeWord() handles non-Latin text with letter case",
+  fn() {
+    assertEquals(capitalizeWord("γράφω"), "Γράφω");
+  },
+});
+
+Deno.test({
+  name: "capitalizeWord() handles non-Latin text without letter case (no-op)",
+  fn() {
+    assertEquals(capitalizeWord("文字"), "文字");
+  },
+});
+
+Deno.test({
+  name: "capitalizeWord() handles non-BMP text (no-op)",
+  fn() {
+    assertEquals(capitalizeWord("💩"), "💩");
+  },
+});

text/to_camel_case.ts

@@ -20,5 +20,5 @@ import { capitalizeWord, splitToWords } from "./_util.ts";
 export function toCamelCase(input: string): string {
   input = input.trim();
   const [first = "", ...rest] = splitToWords(input);
-  return [first.toLocaleLowerCase(), ...rest.map(capitalizeWord)].join("");
+  return [first.toLowerCase(), ...rest.map(capitalizeWord)].join("");
 }

text/to_kebab_case.ts

@@ -19,5 +19,5 @@ import { splitToWords } from "./_util.ts";
  */
 export function toKebabCase(input: string): string {
   input = input.trim();
-  return splitToWords(input).join("-").toLocaleLowerCase();
+  return splitToWords(input).join("-").toLowerCase();
 }

text/to_snake_case.ts

@@ -19,5 +19,5 @@ import { splitToWords } from "./_util.ts";
  */
 export function toSnakeCase(input: string): string {
   input = input.trim();
-  return splitToWords(input).join("_").toLocaleLowerCase();
+  return splitToWords(input).join("_").toLowerCase();
 }

text/unstable_to_constant_case.ts

@@ -21,5 +21,5 @@ import { splitToWords } from "./_util.ts";
  */
 export function toConstantCase(input: string): string {
   input = input.trim();
-  return splitToWords(input).join("_").toLocaleUpperCase();
+  return splitToWords(input).join("_").toUpperCase();
 }