console: refactor to use rest params and template strings

Overall cleanup in code, eliminate reliance on `arguments`.

Benchmarks show that as of v8 5.0.71.32, using rest params + apply
has good performance. The spread operator is not yet well optimized
in v8

```
misc/console.js method=restAndSpread concat=1 n=1000000: 374779.38359
misc/console.js method=restAndSpread concat=0 n=1000000: 375988.30434
misc/console.js method=argumentsAndApply concat=1 n=1000000: 682618.61125
misc/console.js method=argumentsAndApply concat=0 n=1000000: 645093.74443
misc/console.js method=restAndApply concat=1 n=1000000: 682931.41217
misc/console.js method=restAndApply concat=0 n=1000000: 664473.09700
```

PR-URL: https://github.com/nodejs/node/pull/6233
Reviewed-By: Brian White <mscdex@mscdex.net>

benchmark/misc/console.js

@@ -0,0 +1,133 @@
+'use strict';
+
+const common = require('../common.js');
+const assert = require('assert');
+const Writable = require('stream').Writable;
+const util = require('util');
+const v8 = require('v8');
+
+v8.setFlagsFromString('--allow_natives_syntax');
+
+var bench = common.createBenchmark(main, {
+  method: ['restAndSpread',
+           'argumentsAndApply',
+           'restAndApply',
+           'restAndConcat'],
+  concat: [1, 0],
+  n: [1000000]
+});
+
+const nullStream = createNullStream();
+
+function usingRestAndConcat(...args) {
+  nullStream.write('this is ' + args[0] + ' of ' + args[1] + '\n');
+}
+
+function usingRestAndSpreadTS(...args) {
+  nullStream.write(`${util.format(...args)}\n`);
+}
+
+function usingRestAndApplyTS(...args) {
+  nullStream.write(`${util.format.apply(null, args)}\n`);
+}
+
+function usingArgumentsAndApplyTS() {
+  nullStream.write(`${util.format.apply(null, arguments)}\n`);
+}
+
+function usingRestAndSpreadC(...args) {
+  nullStream.write(util.format(...args) + '\n');
+}
+
+function usingRestAndApplyC(...args) {
+  nullStream.write(util.format.apply(null, args) + '\n');
+}
+
+function usingArgumentsAndApplyC() {
+  nullStream.write(util.format.apply(null, arguments) + '\n');
+}
+
+function optimize(method, ...args) {
+  method(...args);
+  eval(`%OptimizeFunctionOnNextCall(${method.name})`);
+  method(...args);
+}
+
+function runUsingRestAndConcat(n) {
+  optimize(usingRestAndConcat, 'a', 1);
+
+  var i = 0;
+  bench.start();
+  for (; i < n; i++)
+    usingRestAndConcat('a', 1);
+  bench.end(n);
+}
+
+function runUsingRestAndSpread(n, concat) {
+
+  const method = concat ? usingRestAndSpreadC : usingRestAndSpreadTS;
+  optimize(method, 'this is %s of %d', 'a', 1);
+
+  var i = 0;
+  bench.start();
+  for (; i < n; i++)
+    method('this is %s of %d', 'a', 1);
+  bench.end(n);
+}
+
+function runUsingRestAndApply(n, concat) {
+
+  const method = concat ? usingRestAndApplyC : usingRestAndApplyTS;
+  optimize(method, 'this is %s of %d', 'a', 1);
+
+  var i = 0;
+  bench.start();
+  for (; i < n; i++)
+    method('this is %s of %d', 'a', 1);
+  bench.end(n);
+}
+
+function runUsingArgumentsAndApply(n, concat) {
+
+  const method = concat ? usingArgumentsAndApplyC : usingArgumentsAndApplyTS;
+  optimize(method, 'this is %s of %d', 'a', 1);
+
+  var i = 0;
+  bench.start();
+  for (; i < n; i++)
+    method('this is %s of %d', 'a', 1);
+  bench.end(n);
+}
+
+function main(conf) {
+  const n = +conf.n;
+  switch (conf.method) {
+    case 'restAndSpread':
+      runUsingRestAndSpread(n, conf.concat);
+      break;
+    case 'restAndApply':
+      runUsingRestAndApply(n, conf.concat);
+      break;
+    case 'argumentsAndApply':
+      runUsingArgumentsAndApply(n, conf.concat);
+      break;
+    case 'restAndConcat':
+      if (conf.concat)
+        runUsingRestAndConcat(n);
+    break;
+    default:
+      throw new Error('Unexpected method');
+  }
+}
+
+function createNullStream() {
+  // Used to approximate /dev/null
+  function NullStream() {
+    Writable.call(this, {});
+  }
+  util.inherits(NullStream, Writable);
+  NullStream.prototype._write = function(cb) {
+    assert.strictEqual(cb.toString(), 'this is a of 1\n');
+  };
+  return new NullStream();
+}

lib/console.js

@@ -35,16 +35,20 @@ function Console(stdout, stderr) {
   }
 }
 
-Console.prototype.log = function() {
-  this._stdout.write(util.format.apply(null, arguments) + '\n');
+
+// As of v8 5.0.71.32, the combination of rest param, template string
+// and .apply(null, args) benchmarks consistently faster than using
+// the spread operator when calling util.format.
+Console.prototype.log = function(...args) {
+  this._stdout.write(`${util.format.apply(null, args)}\n`);
 };
 
 
 Console.prototype.info = Console.prototype.log;
 
 
-Console.prototype.warn = function() {
-  this._stderr.write(util.format.apply(null, arguments) + '\n');
+Console.prototype.warn = function(...args) {
+  this._stderr.write(`${util.format.apply(null, args)}\n`);
 };
 
 
@@ -52,9 +56,8 @@ Console.prototype.error = Console.prototype.warn;
 
 
 Console.prototype.dir = function(object, options) {
-  this._stdout.write(util.inspect(object, util._extend({
-    customInspect: false
-  }, options)) + '\n');
+  options = Object.assign({customInspect: false}, options);
+  this._stdout.write(`${util.inspect(object, options)}\n`);
 };
 
 
@@ -66,7 +69,7 @@ Console.prototype.time = function(label) {
 Console.prototype.timeEnd = function(label) {
   var time = this._times.get(label);
   if (!time) {
-    throw new Error('No such label: ' + label);
+    throw new Error(`No such label: ${label}`);
   }
   const duration = process.hrtime(time);
   const ms = duration[0] * 1000 + duration[1] / 1e6;
@@ -75,24 +78,20 @@ Console.prototype.timeEnd = function(label) {
 };
 
 
-Console.prototype.trace = function trace() {
+Console.prototype.trace = function trace(...args) {
   // TODO probably can to do this better with V8's debug object once that is
   // exposed.
   var err = new Error();
   err.name = 'Trace';
-  err.message = util.format.apply(null, arguments);
+  err.message = util.format.apply(null, args);
   Error.captureStackTrace(err, trace);
   this.error(err.stack);
 };
 
 
-Console.prototype.assert = function(expression) {
+Console.prototype.assert = function(expression, ...args) {
   if (!expression) {
-    const argsLen = arguments.length || 1;
-    const arr = new Array(argsLen - 1);
-    for (var i = 1; i < argsLen; i++)
-      arr[i - 1] = arguments[i];
-    require('assert').ok(false, util.format.apply(null, arr));
+    require('assert').ok(false, util.format.apply(null, args));
   }
 };