Escape - in a way that’s compatible with Unicode patterns

index.js

@@ -1,11 +1,13 @@
 'use strict';
 
-const matchOperatorsRegex = /[|\\{}()[\]^$+*?.-]/g;
-
 module.exports = string => {
 	if (typeof string !== 'string') {
 		throw new TypeError('Expected a string');
 	}
 
-	return string.replace(matchOperatorsRegex, '\\$&');
+	// Escape characters with special meaning either inside or outside character sets.
+	// Use a simple backslash escape when it’s always valid, and a \unnnn escape when the simpler form would be disallowed by Unicode patterns’ stricter grammar.
+	return string
+		.replace(/[|\\{}()[\]^$+*?.]/g, '\\$&')
+		.replace(/-/g, '\\u002d');
 };

test.js

@@ -11,6 +11,13 @@ test('main', t => {
 test('escapes `-`', t => {
 	t.is(
 		escapeStringRegexp('foo - bar'),
-		'foo \\- bar'
+		'foo \\u002d bar'
+	);
+});
+
+test('escapes `-` in a way compatible with the Unicode flag', t => {
+	t.regex(
+		'-',
+		new RegExp(escapeStringRegexp('-'), 'u')
 	);
 });