Create _benchmarks/combine-vs-es6-vs-permutate.md

_benchmarks/combine-vs-es6-vs-permutate.md

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+---
+title: combine vs es6 vs permutate
+setup: |
+  var testArr = [
+  	[void 0, 1, 2, 3],
+  	[void 0, 'slovo', 'b', 'c'],
+  	[void 0, 'x', 'y', 'z']
+  ];
+tests:
+  -
+    name: combine
+    code: |
+      var ret = [[]];
+      for (var i = 0; i < testArr.length; i++) {
+      	var r = [];
+      	var ret_length = ret.length;
+      	for (var j = 0; j < testArr[i].length; j++) {
+      		for (var k = 0; k < ret_length; k++) {
+      			if(testArr[i][j]) {
+      				r[j * ret_length + k] = ret[k].concat(testArr[i][j]);
+      			} else {
+      				r[j * ret_length + k] = ret[k];
+      			}
+      		}
+      	}
+      	ret = r;
+      }
+      return ret;
+  -
+    name: es6
+    code: |
+      const f = (a, b) => [].concat(...a.map(d => b.map(e => [].concat(d, e).filter(Boolean))));
+      const cartesian = (a, b, ...c) => (b ? cartesian(f(a, b), ...c) : a);
+      return cartesian(...testArr);
+  -
+    name: permutate
+    code: |
+      var known = {};
+      return testArr.reduce(function (sum, current) {
+      	var arr = [].concat.apply([], Array(current.length).fill(sum));
+      	var index = 0;
+      	arr.forEach(function (item, i) {
+      		arr[i] = current[index] ? ((item ? item : '') + current[index]) : false;
+      		if (known[arr[i]]) {
+      			arr[i] = false;
+      		}
+      		known[arr[i]] = true;
+      		!((i + 1) % current.length) && index++;
+      		index >= current.length && (index = 0);
+      	});
+      	return sum.concat(current).concat(arr);
+      }, []).filter(Boolean).map(function (i) {
+      	return ('' + i).split('');
+      });
+---
+