Optimize haveIntersection function for better performance

js/helper.js

@@ -1,39 +1,30 @@
 /* use strict-mode provided by ecma-script5, see http://ejohn.org/blog/ecmascript-5-strict-mode-json-and-more/ for details */
-"use strict";
+'use strict';
 
 /*
  * checks, whether two arrays (this and parameter that) have elements in common
  * true, when this is the case
  */
-Array.prototype.haveIntersection = function (that) {
-	var intersect = false;
-	for (var i in this) {
-		for (var j in that) {
-			if (this[i] === that[j] && this.hasOwnProperty(i) && that.hasOwnProperty(j)) {
-				intersect = true;
-				break;
-			}
-		}
-		if (intersect) break;
-	}
-	return intersect;
-};
-/*
- * create Object.create method, if not already existing
- * mainly neccessary because of Opera, which does not implement it yet
- */
-(function () {
-	if (Object.create)
-		return;
-	Object.create = function (o) {
-		if (arguments.length > 1) {
-			throw new Error('Object.create implementation only accepts the first parameter.');
-		}
-		function F() {};
-		F.prototype = o;
-		return new F();
-	};
-})();
+Array.prototype.haveIntersection = (function (that) {
+  let set = new Set(this);
+  return that.some((val) => set.has(val));
+})(
+  /*
+   * create Object.create method, if not already existing
+   * mainly neccessary because of Opera, which does not implement it yet
+   */
+  function () {
+    if (Object.create) return;
+    Object.create = function (o) {
+      if (arguments.length > 1) {
+        throw new Error('Object.create implementation only accepts the first parameter.');
+      }
+      function F() {}
+      F.prototype = o;
+      return new F();
+    };
+  }
+)();
 /*
  * Given an arbitrary number of arrays, these function calculates the Cartesian Product
  * Taken from: http://gotochriswest.com/blog/2011/05/02/cartesian-product-of-multiple-arrays/
@@ -45,33 +36,36 @@ Array.prototype.haveIntersection = function (that) {
  * -	https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/array/foreach
  */
 Array.cartesianProduct = function () {
-	return Array.prototype.reduce.call(arguments, function(previousValue, currentValue) {
-		var ret = [];
-		previousValue.forEach(function(previousValue) {
-			currentValue.forEach(function(currentValue) {
-				ret.push(previousValue.concat([currentValue]));
-			});
-		});
-		return ret;
-	}, [[]]);
+  return Array.prototype.reduce.call(
+    arguments,
+    function (previousValue, currentValue) {
+      var ret = [];
+      previousValue.forEach(function (previousValue) {
+        currentValue.forEach(function (currentValue) {
+          ret.push(previousValue.concat([currentValue]));
+        });
+      });
+      return ret;
+    },
+    [[]]
+  );
 };
 
-
 // specifically for arrays sorted using the same order
 Array.prototype.subsetOfSorted = function (other) {
-	var j = 0;
-	for (var i = 0; i < this.length; i += 1) {
-		while (this[i] !== other[j]) {
-			++j;
-			if (j >= other.length) {
-				return false
-			}
-		}
-	}
-	return true;
+  var j = 0;
+  for (var i = 0; i < this.length; i += 1) {
+    while (this[i] !== other[j]) {
+      ++j;
+      if (j >= other.length) {
+        return false;
+      }
+    }
+  }
+  return true;
 };
 
 /* returns an array's last element */
 Array.prototype.last = function () {
-	return this[this.length - 1];
-}
+  return this[this.length - 1];
+};