Optimise string trimming on JavaScript

Author: richard-viney

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## Unreleased
+
+- The performance of `string.trim`, `string.trim_start`, and `string.trim_end`
+  has been improved on JavaScript.
+
 ## v0.44.0 - 2024-11-25
 
 - The `gleam/queue` module has been deprecated in favour of the `gleam_deque`

src/gleam_stdlib.mjs

@@ -302,19 +302,22 @@ const unicode_whitespaces = [
   "\u2029", // Paragraph separator
 ].join("");
 
-const left_trim_regex = new RegExp(`^([${unicode_whitespaces}]*)`, "g");
-const right_trim_regex = new RegExp(`([${unicode_whitespaces}]*)$`, "g");
+const trim_start_regex = new RegExp(`^[${unicode_whitespaces}]*`);
+const trim_end_regex = new RegExp(`[${unicode_whitespaces}]*$`);
+const trim_regex = new RegExp(
+  `^[${unicode_whitespaces}]*(.*?)[${unicode_whitespaces}]*$`
+);
 
 export function trim(string) {
-  return trim_start(trim_end(string));
+  return string.match(trim_regex)[1];
 }
 
 export function trim_start(string) {
-  return string.replace(left_trim_regex, "");
+  return string.replace(trim_start_regex, "");
 }
 
 export function trim_end(string) {
-  return string.replace(right_trim_regex, "");
+  return string.replace(trim_end_regex, "");
 }
 
 export function bit_array_from_string(string) {

test/gleam/string_test.gleam

@@ -179,6 +179,23 @@ pub fn trim_end_test() {
   |> should.equal("  hats")
 }
 
+pub fn trim_whole_string_test() {
+  let s =
+    "\u{0020}\u{0009}\u{000A}\u{000B}\u{000C}\u{000D}\u{0085}\u{2028}\u{2029}"
+
+  s
+  |> string.trim_start
+  |> should.equal("")
+
+  s
+  |> string.trim_end
+  |> should.equal("")
+
+  s
+  |> string.trim
+  |> should.equal("")
+}
+
 // unicode whitespaces
 pub fn trim_horizontal_tab_test() {
   "hats\u{0009}"