Method to look up the children count of an object

Author: Joris-van-der-Wel

lib/SymbolTree.js

@@ -506,6 +506,27 @@ class SymbolTree {
                 return index;
         }
 
+        /**
+         * Calculate the number of children.
+         *
+         * `O(n)`<br>
+         * `O(1)` (cached)
+         *
+         * @method childrenCount
+         * @memberOf module:symbol-tree#
+         * @param parent
+         * @return {Number}
+         */
+        childrenCount(parent) {
+                const parentNode = this._node(parent);
+
+                if (!parentNode.last) {
+                        return 0;
+                }
+
+                return this.index(parentNode.last) + 1;
+        }
+
         /**
          * Remove the object from this tree.
          * Has no effect if already removed.

test/SymbolTree.js

@@ -960,3 +960,27 @@ test('cached index', function(t) {
 
         t.end();
 });
+
+test('children count', function(t) {
+        // no need to test the caching since we already tested for that in childrenCount
+        const tree = new SymbolTree();
+        const a = {};
+        const aa = {};
+        const ab = {};
+        const aba = {};
+        const ac = {};
+        const b = {};
+
+        tree.insertLast(aa, a);
+        tree.insertLast(ab, a);
+        tree.insertLast(aba, ab);
+        tree.insertLast(ac, a);
+        tree.insertAfter(b, a);
+
+        t.equal(3, tree.childrenCount(a), 'foo');
+        t.equal(0, tree.childrenCount(aa));
+        t.equal(1, tree.childrenCount(ab));
+        t.equal(0, tree.childrenCount(b));
+
+        t.end();
+});