Deprecated: optimize regular expression for $.trim for long sequences of whitespace runs

vlsi · vlsi · commit 39dae7f97de0 · 2022-07-19T17:10:50.000+03:00
Regex imp implementation takes O(N^2) time to trim the string when multiple
adjacent spaces were present.

The new expression require that the "whitespace run" starts from a non-whitespace
to avoid O(N^2) behavior when the engine would try matching "\s$" at each space position.
diff --git a/src/deprecated.js b/src/deprecated.js
@@ -15,7 +15,9 @@ define( [
 
 // Support: Android <=4.0 only
 // Make sure we trim BOM and NBSP
-var rtrim = /^[\s\uFEFF\xA0]+|[\s\uFEFF\xA0]+$/g;
+// Require that the "whitespace run" starts from a non-whitespace
+// to avoid O(N^2) behavior when the engine would try matching "\s$" at each space position.
+var rtrim = /^[\s\uFEFF\xA0]+|([^\s\uFEFF\xA0])[\s\uFEFF\xA0]+$/g;
 
 // Bind a function to a context, optionally partially applying any
 // arguments.
@@ -82,6 +84,6 @@ jQuery.isNumeric = function( obj ) {
 jQuery.trim = function( text ) {
 	return text == null ?
 		"" :
-		( text + "" ).replace( rtrim, "" );
+		( text + "" ).replace( rtrim, "$1" );
 };
 } );
