benchmark: add default configs to buffer benchmark

Add default values to use for `type` and `method` in `buffer` benchmarks
when the provided configuration value is an empty string. This is
primarily useful for testing, so the test can request a single iteration
without having to worry about providing different valid values for the
different benchmarks.

While making this change, some `var` instances in immediately
surrounding code were changed to `const`. In some cases, `var` had been
preserved so that the benchmarks would continue to run in versions of
Node.js prior to 4.0.0. However, now that `const` has been introduced
into the benchmark `common` module, the benchmarks will no longer run
with those versions of Node.js anyway.

PR-URL: https://github.com/nodejs/node/pull/15175
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com

benchmark/buffers/buffer-creation.js

@@ -19,6 +19,7 @@ function main(conf) {
   const len = +conf.len;
   const n = +conf.n;
   switch (conf.type) {
+    case '':
     case 'fast-alloc':
       bench.start();
       for (let i = 0; i < n * 1024; i++) {

benchmark/buffers/buffer-iterate.js

@@ -17,12 +17,13 @@ var methods = {
 };
 
 function main(conf) {
-  var len = +conf.size;
+  const len = +conf.size;
-  var clazz = conf.type === 'fast' ? Buffer : SlowBuffer;
+  const clazz = conf.type === 'fast' ? Buffer : SlowBuffer;
-  var buffer = new clazz(len);
+  const buffer = new clazz(len);
   buffer.fill(0);
 
-  methods[conf.method](buffer, conf.n);
+  const method = conf.method || 'for';
+  methods[method](buffer, conf.n);
 }
 
 

benchmark/buffers/buffer-read.js

@@ -26,14 +26,15 @@ var bench = common.createBenchmark(main, {
 });
 
 function main(conf) {
-  var noAssert = conf.noAssert === 'true';
+  const noAssert = conf.noAssert === 'true';
-  var len = +conf.millions * 1e6;
+  const len = +conf.millions * 1e6;
-  var clazz = conf.buf === 'fast' ? Buffer : require('buffer').SlowBuffer;
+  const clazz = conf.buf === 'fast' ? Buffer : require('buffer').SlowBuffer;
-  var buff = new clazz(8);
+  const buff = new clazz(8);
-  var fn = `read${conf.type}`;
+  const type = conf.type || 'UInt8';
+  const fn = `read${type}`;
 
   buff.writeDoubleLE(0, 0, noAssert);
-  var testFunction = new Function('buff', `
+  const testFunction = new Function('buff', `
     for (var i = 0; i !== ${len}; i++) {
       buff.${fn}(0, ${JSON.stringify(noAssert)});
     }

benchmark/buffers/buffer-swap.js

@@ -73,7 +73,7 @@ function genMethod(method) {
 }
 
 function main(conf) {
-  const method = conf.method;
+  const method = conf.method || 'swap16';
   const len = conf.len | 0;
   const n = conf.n | 0;
   const aligned = conf.aligned || 'true';

benchmark/buffers/buffer-write.js

@@ -46,11 +46,12 @@ var mod = {
 };
 
 function main(conf) {
-  var noAssert = conf.noAssert === 'true';
+  const noAssert = conf.noAssert === 'true';
-  var len = +conf.millions * 1e6;
+  const len = +conf.millions * 1e6;
-  var clazz = conf.buf === 'fast' ? Buffer : require('buffer').SlowBuffer;
+  const clazz = conf.buf === 'fast' ? Buffer : require('buffer').SlowBuffer;
-  var buff = new clazz(8);
+  const buff = new clazz(8);
-  var fn = `write${conf.type}`;
+  const type = conf.type || 'UInt8';
+  const fn = `write${type}`;
 
   if (/Int/.test(fn))
     benchInt(buff, fn, len, noAssert);

benchmark/buffers/dataview-set.js

@@ -40,11 +40,12 @@ var mod = {
 };
 
 function main(conf) {
-  var len = +conf.millions * 1e6;
+  const len = +conf.millions * 1e6;
-  var ab = new ArrayBuffer(8);
+  const ab = new ArrayBuffer(8);
-  var dv = new DataView(ab, 0, 8);
+  const dv = new DataView(ab, 0, 8);
-  var le = /LE$/.test(conf.type);
+  const type = conf.type || 'Uint8';
-  var fn = `set${conf.type.replace(/[LB]E$/, '')}`;
+  const le = /LE$/.test(type);
+  const fn = `set${type.replace(/[LB]E$/, '')}`;
 
   if (/int/i.test(fn))
     benchInt(dv, fn, len, le);