add fill unique lib function,

 - useful to fill fullLayout._modules and
   fullLayout._basePlotModules

Author: etpinard

src/lib/index.js

@@ -335,6 +335,23 @@ lib.noneOrAll = function(containerIn, containerOut, attrList) {
     }
 };
 
+/**
+ * Fill with unique items
+ *
+ * @param {array} array
+ *  array to be filled
+ * @param {any} item
+ *  item to be or not to be inserted
+ * @return {array}
+ *  ref to array (now possibly containing one more item)
+ *
+ */
+lib.fillUnique = function(array, item) {
+    if(item && array.indexOf(item) === -1) array.push(item);
+
+    return array;
+};
+
 lib.mergeArray = function(traceAttr, cd, cdAttr) {
     if(Array.isArray(traceAttr)) {
         var imax = Math.min(traceAttr.length, cd.length);

test/jasmine/tests/lib_test.js

@@ -770,4 +770,44 @@ describe('Test lib.js:', function() {
         });
     });
 
+    describe('fillUnique', function() {
+
+        beforeEach(function() {
+            this.obj = { a: 'A' };
+            this.array = ['a', 'b', 'c', this.obj];
+        });
+
+        it('should fill new items in array', function() {
+            var out = Lib.fillUnique(this.array, 'd');
+
+            expect(this.array).toEqual(['a', 'b', 'c', { a: 'A' }, 'd']);
+            expect(this.array).toBe(out);
+        });
+
+        it('should ignore falsy items', function() {
+            Lib.fillUnique(this.array, false);
+            expect(this.array).toEqual(['a', 'b', 'c', { a: 'A' }]);
+
+            Lib.fillUnique(this.array, undefined);
+            expect(this.array).toEqual(['a', 'b', 'c', { a: 'A' }]);
+
+            Lib.fillUnique(this.array, 0);
+            expect(this.array).toEqual(['a', 'b', 'c', { a: 'A' }]);
+
+            Lib.fillUnique(this.array, null);
+            expect(this.array).toEqual(['a', 'b', 'c', { a: 'A' }]);
+
+            Lib.fillUnique(this.array, '');
+            expect(this.array).toEqual(['a', 'b', 'c', { a: 'A' }]);
+        });
+
+        it('should ignore item already in array', function() {
+            Lib.fillUnique(this.array, 'a');
+            expect(this.array).toEqual(['a', 'b', 'c', { a: 'A' }]);
+
+            Lib.fillUnique(this.array, this.obj);
+            expect(this.array).toEqual(['a', 'b', 'c', { a: 'A' }]);
+        });
+    });
+
 });