benchmark: add microbenchmarks for ES Map

PR-URL: https://github.com/nodejs/node/pull/7581
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Franziska Hinkelmann <ranziska.hinkelmann@gmail.com>

benchmark/es/map-bench.js

@@ -0,0 +1,96 @@
+'use strict';
+
+const common = require('../common.js');
+const assert = require('assert');
+
+const bench = common.createBenchmark(main, {
+  method: ['object', 'nullProtoObject', 'fakeMap', 'map'],
+  millions: [1]
+});
+
+function runObject(n) {
+  const m = {};
+  var i = 0;
+  bench.start();
+  for (; i < n; i++) {
+    m['i' + i] = i;
+    m['s' + i] = String(i);
+    assert.equal(m['i' + i], m['s' + i]);
+    m['i' + i] = undefined;
+    m['s' + i] = undefined;
+  }
+  bench.end(n / 1e6);
+}
+
+function runNullProtoObject(n) {
+  const m = Object.create(null);
+  var i = 0;
+  bench.start();
+  for (; i < n; i++) {
+    m['i' + i] = i;
+    m['s' + i] = String(i);
+    assert.equal(m['i' + i], m['s' + i]);
+    m['i' + i] = undefined;
+    m['s' + i] = undefined;
+  }
+  bench.end(n / 1e6);
+}
+
+function fakeMap() {
+  const m = {};
+  return {
+    get(key) { return m['$' + key]; },
+    set(key, val) { m['$' + key] = val; },
+    get size() { return Object.keys(m).length; },
+    has(key) { return Object.prototype.hasOwnProperty.call(m, '$' + key); }
+  };
+}
+
+function runFakeMap(n) {
+  const m = fakeMap();
+  var i = 0;
+  bench.start();
+  for (; i < n; i++) {
+    m.set('i' + i, i);
+    m.set('s' + i, String(i));
+    assert.equal(m.get('i' + i), m.get('s' + i));
+    m.set('i' + i, undefined);
+    m.set('s' + i, undefined);
+  }
+  bench.end(n / 1e6);
+}
+
+function runMap(n) {
+  const m = new Map();
+  var i = 0;
+  bench.start();
+  for (; i < n; i++) {
+    m.set('i' + i, i);
+    m.set('s' + i, String(i));
+    assert.equal(m.get('i' + i), m.get('s' + i));
+    m.set('i' + i, undefined);
+    m.set('s' + i, undefined);
+  }
+  bench.end(n / 1e6);
+}
+
+function main(conf) {
+  const n = +conf.millions * 1e6;
+
+  switch (conf.method) {
+    case 'object':
+      runObject(n);
+      break;
+    case 'nullProtoObject':
+      runNullProtoObject(n);
+      break;
+    case 'fakeMap':
+      runFakeMap(n);
+      break;
+    case 'map':
+      runMap(n);
+      break;
+    default:
+      throw new Error('Unexpected method');
+  }
+}