improve benchmark, optimize for case 3 too.

Author: Uzlopak

benchmark/error/format-list.js

@@ -9,20 +9,36 @@ const bench = common.createBenchmark(main, {
     'a',
     'a,b',
     'a,b,c',
+    'a,b,c,d',
+  ],
+  type: [
+    'undefined',
+    'and',
+    'or',
   ],
 }, {
   flags: ['--expose-internals'],
 });
 
-function main({ n, input }) {
+function main({ n, input, type }) {
   const {
     formatList,
   } = require('internal/errors');
 
   const list = input.split(',');
+
+  if (type === 'undefined') {
+    bench.start();
+    for (let i = 0; i < n; ++i) {
+      formatList(list);
+    }
+    bench.end(n);
+    return;
+  }
+
   bench.start();
   for (let i = 0; i < n; ++i) {
-    formatList(list);
+    formatList(list, type);
   }
   bench.end(n);
 }

lib/internal/errors.js

@@ -906,6 +906,7 @@ function formatList(array, type = 'and') {
     case 0: return '';
     case 1: return `${array[0]}`;
     case 2: return `${array[0]} ${type} ${array[1]}`;
+    case 3: return `${array[0]}, ${array[1]}, ${type} ${array[2]}`;
     default:
       return `${ArrayPrototypeJoin(ArrayPrototypeSlice(array, 0, -1), ', ')}, ${type} ${array[array.length - 1]}`;
   }

test/parallel/test-error-format-list.js

@@ -11,7 +11,7 @@ if (!common.hasIntl) common.skip('missing Intl');
   const and = new Intl.ListFormat('en', { style: 'long', type: 'conjunction' });
   const or = new Intl.ListFormat('en', { style: 'long', type: 'disjunction' });
 
-  const input = ['apple', 'banana', 'orange'];
+  const input = ['apple', 'banana', 'orange', 'pear'];
   for (let i = 0; i < input.length; i++) {
     const slicedInput = input.slice(0, i);
     strictEqual(formatList(slicedInput), and.format(slicedInput));