walkUp function

src/index-fn.js

@@ -9,3 +9,4 @@ export {default as closest}       from "./closest.js";
 export {default as find}          from "./find.js";
 export {default as map}           from "./map.js";
 export {default as walk}          from "./walk.js";
+export {default as walkUp}        from "./walkUp.js";

src/walkUp.js

@@ -0,0 +1,22 @@
+import * as parents from "./parents.js";
+
+/**
+ * Walk up the tree from the given node, calling the callback on each node.
+ * @param {object} node 
+ * @param {function} callback 
+ * @returns {any} The first non-undefined value returned by the callback, or the highest ancestor node if no undefined value is ever returned.
+ */
+export default function walkUp (node, callback) {
+    let previousNode;
+    while (node) {
+        const ret = callback(node);
+        if (ret !== undefined) {
+            return ret;
+        }
+        previousNode = node;
+        const parent = parents.getParent.call(this, node);
+        // TODO: what should happen if parent is undefined (meaning no parent pointers have been set?)
+        node = parent;
+    }
+    return previousNode;
+}

test/walkUp.js

@@ -0,0 +1,26 @@
+import walkUp from "../src/walkUp.js";
+import trees from "./utils/trees.js";
+import updateParents from "../src/updateParents.js";
+import copy from "./utils/copy.js"
+
+const tree = copy(trees[0]);
+updateParents(tree);
+
+export default {
+	name: "walkUp()",
+	run (node, cb) {
+		return walkUp(node, cb);
+	},
+	tests: [
+		{
+            name: "No callback",
+			args: [tree.right, () => {}],
+			expect: tree
+		},
+        {
+            name: "Callback returns a value",
+            args: [tree.right, n => n.name === "1" ? n : undefined],
+            expect: tree
+        }
+	]
+};