Improve performance by adding fast path for strings without ANSI codes (#54)

Author: privatenumber

index.js

@@ -7,6 +7,11 @@ export default function stripAnsi(string) {
 		throw new TypeError(`Expected a \`string\`, got \`${typeof string}\``);
 	}
 
+	// Fast path: ANSI codes require ESC (7-bit) or CSI (8-bit) introducer
+	if (!string.includes('\u001B') && !string.includes('\u009B')) {
+		return string;
+	}
+
 	// Even though the regex is global, we don't need to reset the `.lastIndex`
 	// because unlike `.exec()` and `.test()`, `.replace()` does it automatically
 	// and doing it manually has a performance penalty.

test.js

@@ -22,3 +22,15 @@ test('strip OSC sequence with BEL terminator', t => {
 	const output = stripAnsi(input);
 	t.is(output, 'ABC\r\n');
 });
+
+test('strip color from string using 8-bit CSI introducer', t => {
+	t.is(stripAnsi('\u009B31mfoo\u009B39m'), 'foo');
+});
+
+test('return string as-is if no ANSI codes', t => {
+	t.is(stripAnsi('foo bar'), 'foo bar');
+});
+
+test('return empty string as-is', t => {
+	t.is(stripAnsi(''), '');
+});