benchmark: benchmark comparing forEach with for

PR-URL: https://github.com/nodejs/node/pull/11582
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

benchmark/es/foreach-bench.js

@@ -0,0 +1,82 @@
+'use strict';
+
+const common = require('../common.js');
+
+const bench = common.createBenchmark(main, {
+  method: ['for', 'for-of', 'for-in', 'forEach'],
+  count: [5, 10, 20, 100],
+  millions: [5]
+});
+
+function useFor(n, items, count) {
+  var i, j;
+  bench.start();
+  for (i = 0; i < n; i++) {
+    for (j = 0; j < count; j++) {
+      /* eslint-disable no-unused-vars */
+      var item = items[j];
+      /* esline-enable no-unused-vars */
+    }
+  }
+  bench.end(n / 1e6);
+}
+
+function useForOf(n, items) {
+  var i, item;
+  bench.start();
+  for (i = 0; i < n; i++) {
+    for (item of items) {}
+  }
+  bench.end(n / 1e6);
+}
+
+function useForIn(n, items) {
+  var i, j, item;
+  bench.start();
+  for (i = 0; i < n; i++) {
+    for (j in items) {
+      /* eslint-disable no-unused-vars */
+      item = items[j];
+      /* esline-enable no-unused-vars */
+    }
+  }
+  bench.end(n / 1e6);
+}
+
+function useForEach(n, items) {
+  var i;
+  bench.start();
+  for (i = 0; i < n; i++) {
+    items.forEach((item) => {});
+  }
+  bench.end(n / 1e6);
+}
+
+function main(conf) {
+  const n = +conf.millions * 1e6;
+  const count = +conf.count;
+
+  const items = new Array(count);
+  var i;
+  var fn;
+  for (i = 0; i < count; i++)
+    items[i] = i;
+
+  switch (conf.method) {
+    case 'for':
+      fn = useFor;
+      break;
+    case 'for-of':
+      fn = useForOf;
+      break;
+    case 'for-in':
+      fn = useForIn;
+      break;
+    case 'forEach':
+      fn = useForEach;
+      break;
+    default:
+      throw new Error('Unexpected method');
+  }
+  fn(n, items, count);
+}