Add util functions for set operations

modules/util/array.js

@@ -0,0 +1,46 @@
+
+// http://2ality.com/2015/01/es6-set-operations.html
+
+// Difference (a \ b): create a set that contains those elements of set a that are not in set b.
+// This operation is also sometimes called minus (-).
+// var a = [1,2,3];
+// var b = [4,3,2];
+// utilArrayDifference(a, b)
+//   [1]
+// utilArrayDifference(b, a)
+//   [4]
+export function utilArrayDifference(a, b) {
+    var other = new Set(b);
+    return Array.from(new Set(a))
+        .filter(function(v) { return !other.has(v); });
+}
+
+// Intersection (a ∩ b): create a set that contains those elements of set a that are also in set b.
+// var a = [1,2,3];
+// var b = [4,3,2];
+// utilArrayIntersection(a, b)
+//   [2,3]
+export function utilArrayIntersection(a, b) {
+    var other = new Set(b);
+    return Array.from(new Set(a))
+        .filter(function(v) { return other.has(v); });
+}
+
+// Union (a ∪ b): create a set that contains the elements of both set a and set b.
+// var a = [1,2,3];
+// var b = [4,3,2];
+// utilArrayUnion(a, b)
+//   [1,2,3,4]
+export function utilArrayUnion(a, b) {
+    var result = new Set(a);
+    b.forEach(function(v) { result.add(v); });
+    return Array.from(result);
+}
+
+// Returns an Array with all the duplicates removed
+// var a = [1,1,2,3,3];
+// utilArrayUniq(a)
+//   [1,2,3]
+export function utilArrayUniq(a) {
+    return Array.from(new Set(a));
+}

modules/util/index.js

@@ -1,3 +1,7 @@
+export { utilArrayDifference } from './array';
+export { utilArrayIntersection } from './array';
+export { utilArrayUnion } from './array';
+export { utilArrayUniq } from './array';
 export { utilAsyncMap } from './util';
 export { utilCallWhenIdle } from './call_when_idle';
 export { utilCleanTags } from './clean_tags';

test/index.html

@@ -143,8 +143,10 @@
     <script src='spec/ui/fields/localized.js'></script>
     <script src='spec/ui/fields/wikipedia.js'></script>
 
+    <script src='spec/util/array.js'></script>
     <script src='spec/util/clean_tags.js'></script>
     <script src='spec/util/keybinding.js'></script>
+    <script src='spec/util/object.js'></script>
     <script src='spec/util/session_mutex.js'></script>
     <script src='spec/util/util.js'></script>
 

test/spec/util/array.js

@@ -0,0 +1,43 @@
+describe('iD.utilArrayDifference', function() {
+    it('returns set difference', function() {
+        var a = [1, 2, 3];
+        var b = [4, 3, 2];
+        expect(iD.utilArrayDifference([], [])).to.eql([]);
+        expect(iD.utilArrayDifference([], a)).to.eql([]);
+        expect(iD.utilArrayDifference(a, [])).to.have.members([1, 2, 3]);
+        expect(iD.utilArrayDifference(a, b)).to.have.members([1]);
+        expect(iD.utilArrayDifference(b, a)).to.have.members([4]);
+    });
+});
+
+describe('iD.utilArrayIntersection', function() {
+    it('returns set intersection', function() {
+        var a = [1, 2, 3];
+        var b = [4, 3, 2];
+        expect(iD.utilArrayIntersection([], [])).to.eql([]);
+        expect(iD.utilArrayIntersection([], a)).to.eql([]);
+        expect(iD.utilArrayIntersection(a, [])).to.eql([]);
+        expect(iD.utilArrayIntersection(a, b)).to.have.members([2, 3]);
+        expect(iD.utilArrayIntersection(b, a)).to.have.members([2, 3]);
+    });
+});
+
+describe('iD.utilArrayUnion', function() {
+    it('returns set union', function() {
+        var a = [1, 2, 3];
+        var b = [4, 3, 2];
+        expect(iD.utilArrayUnion([], [])).to.eql([]);
+        expect(iD.utilArrayUnion([], a)).to.have.members([1, 2, 3]);
+        expect(iD.utilArrayUnion(a, [])).to.have.members([1, 2, 3]);
+        expect(iD.utilArrayUnion(a, b)).to.have.members([1, 2, 3, 4]);
+        expect(iD.utilArrayUnion(b, a)).to.have.members([1, 2, 3, 4]);
+    });
+});
+
+describe('iD.utilArrayUniq', function() {
+    it('returns unique values', function() {
+        var a = [1, 1, 2, 3, 3];
+        expect(iD.utilArrayUniq([])).to.eql([]);
+        expect(iD.utilArrayUniq(a)).to.have.members([1, 2, 3]);
+    });
+});