remove variability on string generation (#50)

Fixes #47

bench.js

@@ -15,14 +15,10 @@ const dummyConsole = new Console(fs.createWriteStream('/dev/null'))
 
 const MAX = 10000
 
-function str () {
-  let res = ''
+let str = ''
 
-  for (let i = 0; i < 10; i++) {
-    res += 'hello'
-  }
-
-  return res
+for (let i = 0; i < 10; i++) {
+  str += 'hello'
 }
 
 setTimeout(doBench, 100)
@@ -31,36 +27,36 @@ const run = bench([
   function benchSonic (cb) {
     sonic.once('drain', cb)
     for (let i = 0; i < MAX; i++) {
-      sonic.write(str())
+      sonic.write(str)
     }
   },
   function benchSonicSync (cb) {
     sonicSync.once('drain', cb)
     for (let i = 0; i < MAX; i++) {
-      sonicSync.write(str())
+      sonicSync.write(str)
     }
   },
   function benchSonic4k (cb) {
     sonic4k.once('drain', cb)
     for (let i = 0; i < MAX; i++) {
-      sonic4k.write(str())
+      sonic4k.write(str)
     }
   },
   function benchSonicSync4k (cb) {
     sonicSync4k.once('drain', cb)
     for (let i = 0; i < MAX; i++) {
-      sonicSync4k.write(str())
+      sonicSync4k.write(str)
     }
   },
   function benchCore (cb) {
     core.once('drain', cb)
     for (let i = 0; i < MAX; i++) {
-      core.write(str())
+      core.write(str)
     }
   },
   function benchConsole (cb) {
     for (let i = 0; i < MAX; i++) {
-      dummyConsole.log(str())
+      dummyConsole.log(str)
     }
     setImmediate(cb)
   }