benchmark: replace [].join() with ''.repeat()

Also add a benchmark to compare both ways to create strings.

PR-URL: nodejs#12170
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

benchmark/crypto/cipher-stream.js

@@ -40,11 +40,11 @@ function main(conf) {
   var encoding;
   switch (conf.type) {
     case 'asc':
-      message = new Array(conf.len + 1).join('a');
+      message = 'a'.repeat(conf.len);
       encoding = 'ascii';
       break;
     case 'utf':
-      message = new Array(conf.len / 2 + 1).join('ü');
+      message = 'ü'.repeat(conf.len / 2);
       encoding = 'utf8';
       break;
     case 'buf':

benchmark/crypto/hash-stream-creation.js

@@ -25,11 +25,11 @@ function main(conf) {
   var encoding;
   switch (conf.type) {
     case 'asc':
-      message = new Array(conf.len + 1).join('a');
+      message = 'a'.repeat(conf.len);
       encoding = 'ascii';
       break;
     case 'utf':
-      message = new Array(conf.len / 2 + 1).join('ü');
+      message = 'ü'.repeat(conf.len / 2);
       encoding = 'utf8';
       break;
     case 'buf':

benchmark/crypto/hash-stream-throughput.js

@@ -24,11 +24,11 @@ function main(conf) {
   var encoding;
   switch (conf.type) {
     case 'asc':
-      message = new Array(conf.len + 1).join('a');
+      message = 'a'.repeat(conf.len);
       encoding = 'ascii';
       break;
     case 'utf':
-      message = new Array(conf.len / 2 + 1).join('ü');
+      message = 'ü'.repeat(conf.len / 2);
       encoding = 'utf8';
       break;
     case 'buf':

benchmark/es/string-repeat.js

@@ -0,0 +1,35 @@
+'use strict';
+
+const assert = require('assert');
+const common = require('../common.js');
+
+const configs = {
+  n: [1e3],
+  mode: ['Array', 'repeat'],
+  encoding: ['ascii', 'utf8'],
+  size: [1e1, 1e3, 1e6],
+};
+
+const bench = common.createBenchmark(main, configs);
+
+function main(conf) {
+  const n = +conf.n;
+  const size = +conf.size;
+  const character = conf.encoding === 'ascii' ? 'a' : '\ud83d\udc0e'; // '🐎'
+
+  let str;
+
+  if (conf.mode === 'Array') {
+    bench.start();
+    for (let i = 0; i < n; i++)
+      str = new Array(size + 1).join(character);
+    bench.end(n);
+  } else {
+    bench.start();
+    for (let i = 0; i < n; i++)
+      str = character.repeat(size);
+    bench.end(n);
+  }
+
+  assert.strictEqual([...str].length, size);
+}

benchmark/fs/write-stream-throughput.js

@@ -24,11 +24,11 @@ function main(conf) {
       chunk = Buffer.alloc(size, 'b');
       break;
     case 'asc':
-      chunk = new Array(size + 1).join('a');
+      chunk = 'a'.repeat(size);
       encoding = 'ascii';
       break;
     case 'utf':
-      chunk = new Array(Math.ceil(size / 2) + 1).join('ü');
+      chunk = 'ü'.repeat(Math.ceil(size / 2));
       encoding = 'utf8';
       break;
     default:

benchmark/http/client-request-body.js

@@ -23,10 +23,10 @@ function main(conf) {
       break;
     case 'utf':
       encoding = 'utf8';
-      chunk = new Array(len / 2 + 1).join('ü');
+      chunk = 'ü'.repeat(len / 2);
       break;
     case 'asc':
-      chunk = new Array(len + 1).join('a');
+      chunk = 'a'.repeat(len);
       break;
   }
 

benchmark/http/end-vs-write-end.js

@@ -26,10 +26,10 @@ function main(conf) {
       chunk = Buffer.alloc(len, 'x');
       break;
     case 'utf':
-      chunk = new Array(len / 2 + 1).join('ü');
+      chunk = 'ü'.repeat(len / 2);
       break;
     case 'asc':
-      chunk = new Array(len + 1).join('a');
+      chunk = 'a'.repeat(len);
       break;
   }
 

benchmark/net/net-c2s-cork.js

@@ -27,11 +27,11 @@ function main(conf) {
       break;
     case 'utf':
       encoding = 'utf8';
-      chunk = new Array(len / 2 + 1).join('ü');
+      chunk = 'ü'.repeat(len / 2);
       break;
     case 'asc':
       encoding = 'ascii';
-      chunk = new Array(len + 1).join('x');
+      chunk = 'x'.repeat(len);
       break;
     default:
       throw new Error('invalid type: ' + type);

benchmark/net/net-c2s.js

@@ -27,11 +27,11 @@ function main(conf) {
       break;
     case 'utf':
       encoding = 'utf8';
-      chunk = new Array(len / 2 + 1).join('ü');
+      chunk = 'ü'.repeat(len / 2);
       break;
     case 'asc':
       encoding = 'ascii';
-      chunk = new Array(len + 1).join('x');
+      chunk = 'x'.repeat(len);
       break;
     default:
       throw new Error('invalid type: ' + type);

benchmark/net/net-pipe.js

@@ -27,11 +27,11 @@ function main(conf) {
       break;
     case 'utf':
       encoding = 'utf8';
-      chunk = new Array(len / 2 + 1).join('ü');
+      chunk = 'ü'.repeat(len / 2);
       break;
     case 'asc':
       encoding = 'ascii';
-      chunk = new Array(len + 1).join('x');
+      chunk = 'x'.repeat(len);
       break;
     default:
       throw new Error('invalid type: ' + type);

benchmark/net/net-s2c.js

@@ -27,11 +27,11 @@ function main(conf) {
       break;
     case 'utf':
       encoding = 'utf8';
-      chunk = new Array(len / 2 + 1).join('ü');
+      chunk = 'ü'.repeat(len / 2);
       break;
     case 'asc':
       encoding = 'ascii';
-      chunk = new Array(len + 1).join('x');
+      chunk = 'x'.repeat(len);
       break;
     default:
       throw new Error('invalid type: ' + type);

benchmark/net/tcp-raw-c2s.js

@@ -83,10 +83,10 @@ function client() {
       chunk = Buffer.alloc(len, 'x');
       break;
     case 'utf':
-      chunk = new Array(len / 2 + 1).join('ü');
+      chunk = 'ü'.repeat(len / 2);
       break;
     case 'asc':
-      chunk = new Array(len + 1).join('x');
+      chunk = 'x'.repeat(len);
       break;
     default:
       throw new Error('invalid type: ' + type);

benchmark/net/tcp-raw-pipe.js

@@ -80,10 +80,10 @@ function client() {
       chunk = Buffer.alloc(len, 'x');
       break;
     case 'utf':
-      chunk = new Array(len / 2 + 1).join('ü');
+      chunk = 'ü'.repeat(len / 2);
       break;
     case 'asc':
-      chunk = new Array(len + 1).join('x');
+      chunk = 'x'.repeat(len);
       break;
     default:
       throw new Error('invalid type: ' + type);

benchmark/net/tcp-raw-s2c.js

@@ -54,10 +54,10 @@ function server() {
         chunk = Buffer.alloc(len, 'x');
         break;
       case 'utf':
-        chunk = new Array(len / 2 + 1).join('ü');
+        chunk = 'ü'.repeat(len / 2);
         break;
       case 'asc':
-        chunk = new Array(len + 1).join('x');
+        chunk = 'x'.repeat(len);
         break;
       default:
         throw new Error('invalid type: ' + type);

benchmark/tls/throughput.js

@@ -26,11 +26,11 @@ function main(conf) {
       chunk = Buffer.alloc(size, 'b');
       break;
     case 'asc':
-      chunk = new Array(size + 1).join('a');
+      chunk = 'a'.repeat(size);
       encoding = 'ascii';
       break;
     case 'utf':
-      chunk = new Array(size / 2 + 1).join('ü');
+      chunk = 'ü'.repeat(size / 2);
       encoding = 'utf8';
       break;
     default: