add benchmark about array concat

.npmignore

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

benchmark/.eslintrc

@@ -0,0 +1,5 @@
+{
+    "rules": {
+        "no-console": 0,
+    },
+}

benchmark/arraying.js

@@ -0,0 +1,142 @@
+'use strict';
+
+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
+
+var singles = function singles(fn) {
+    return function () {
+        return fn('1', '2');
+    };
+};
+
+var arrayThenSingle = function arrayThenSingle(fn) {
+    return function () {
+        return fn([
+            '1', '11', '111'
+        ], '2');
+    };
+};
+
+var singleThenArray = function singleThenArray(fn) {
+    return function () {
+        return fn('1', [
+            '2', '22', '222'
+        ]);
+    };
+};
+
+var arrays = function arrays(fn) {
+    return function () {
+        return fn([
+            '1', '11', '111'
+        ], [
+            '2', '22', '222'
+        ]);
+    };
+};
+
+var methods = [
+    function original(a, b) {
+        return [].concat(a, 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) {
+            if (secondIsArray) {
+                a.push.apply(a, b);
+            } else {
+                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;
+
+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 += 1;
+    }
+});
+
+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": "^13.0.0",
+        "benchmark": "^2.1.4",
         "browserify": "^16.2.2",
+        "comma-number": "^2.0.0",
+        "console.table": "^0.10.0",
         "covert": "^1.1.0",
         "editorconfig-tools": "^0.1.1",
         "eslint": "^5.6.0",