add benchmark about array concat

.npmignore

@@ -2,3 +2,4 @@ bower.json
 component.json
 .npmignore
 .travis.yml
+benchmark/

benchmark/arraying.js

@@ -0,0 +1,127 @@
+require('console.table')
+
+var comma = require('comma-number')
+var Benchmark = require('benchmark')
+
+Benchmark.options.initCount  = 100
+Benchmark.options.minSamples = 100
+
+// useful when altering tests, causes thing to run quickly
+// Benchmark.options.initCount = 1
+// Benchmark.options.minSamples = 1
+// Benchmark.options.minTime = -1
+// Benchmark.options.maxTime = -1
+
+function singles(fn) {
+  return function() {
+    return fn('1', '2')
+  }
+}
+
+function arrayThenSingle(fn) {
+  return function() {
+    return fn(['1', '11', '111'], '2')
+  }
+}
+
+function singleThenArray(fn) {
+  return function() {
+    return fn('1', ['2', '22', '222'])
+  }
+}
+
+function arrays(fn) {
+  return function() {
+    return fn(['1', '11', '111'], ['2', '22', '222'])
+  }
+}
+
+var methods = [
+  function original(a, b) {
+    return [].concat(a).concat(b)
+  },
+
+  function consolidated(a, b) {
+    return [].concat(a, b)
+  },
+
+  function awkward(a, b) {
+    return Array.prototype.concat(a, b)
+  },
+
+  // this isn't able to handle the second arg being an array.
+  function halfway(a, b) {
+    if (Array.isArray(a)) {
+      a.push(b)
+      return a
+    } else {
+      return [a, b]
+    }
+  },
+
+  function mutating(a, b) {
+    // we always use both of these, so, let's calculate them now
+    var firstIsArray  = Array.isArray(a);
+    var secondIsArray = Array.isArray(b);
+
+    // mutate `a` to append `b` and then return it
+    if (firstIsArray) {
+        secondIsArray ? a.push.apply(a, b) : a.push(b)
+        return a
+    }
+
+    // mutate `b` to prepend `a` and then return it
+    if (secondIsArray) {
+        b.unshift(a)
+        return b
+    }
+
+    // neither are arrays, so, create a new array with both
+    return [a, b]
+  }
+]
+
+methods[0].style = '[].concat(a).concat(b)'
+methods[1].style = '[].concat(a, b)'
+methods[2].style = 'Array.prototype.concat(a, b)'
+methods[3].style = 'Array.isArray halfway'
+methods[4].style = 'Array.isArray both'
+
+var suite = new Benchmark.Suite
+var results = []
+
+methods.forEach(function(method, index) {
+  results.push([method.style])
+
+  suite.add(method.style + ' with 2 non-arrays', singles(method))
+  suite.add(method.style + ' with an array then a non-array', arrayThenSingle(method))
+
+  if (index !== 3) {
+    suite.add(method.style + ' with a non-array then an array', singleThenArray(method))
+    suite.add(method.style + ' with 2 arrays', arrays(method))
+  }
+})
+
+var row = 0
+var column = 0
+
+suite.on('cycle', function(event) {
+  var its = event.target
+
+  console.log('completed', its.name)
+
+  results[row].push(comma(its.hz.toFixed(0)) + ' (+-' + its.stats.rme.toFixed(2) + '%)')
+
+  if (results[row].length === 5 || (row === 3 && results[row].length === 3)) {
+    row++
+  }
+})
+
+suite.on('complete', function() {
+  console.log()
+  console.table(['Name', '" / "', '[] / "', '" / []', '[] / []'], results)
+})
+
+suite.run({
+  async: false
+})

package.json

@@ -25,7 +25,10 @@
   "dependencies": {},
   "devDependencies": {
     "@ljharb/eslint-config": "^9.0.1",
+    "benchmark": "^2.1.2",
     "browserify": "^13.1.1",
+    "comma-number": "^1.1.0",
+    "console.table": "^0.8.0",
     "covert": "^1.1.0",
     "eslint": "^3.12.2",
     "evalmd": "^0.0.17",