Add expandNodesToLevel utility

Resolves #244.

Author: jakezatecky

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 * [#182]: Add `direction` property to support RTL languages
 * [#211]: Throw an error when nodes have duplicate values
+* [#244]: Add `expandNodesToLevel` utility
 
 ## [v1.6.0](https://github.com/jakezatecky/react-checkbox-tree/compare/v1.5.0...v1.6.0) (2019-12-11)
 

README.md

@@ -135,6 +135,23 @@ import { FontAwesomeIcon } from '@fortawesome/react-fontawesome'
 />
 ```
 
+### Utility Functions
+
+In addition to the `CheckboxTree` component, additional utility functions are available to set the initial state of the tree.
+
+#### `expandNodesToLevel(nodes, targetLevel)`
+
+Creates a list of all parent node keys until `targetLevel`.
+
+Arguments:
+
+* `nodes` (`Array`): The same array of nodes passed into the main `CheckboxTree` component
+* `targetLevel` (`number`): The maximum expansion depth. Use `Infinity` for maximum depth.
+
+Returns:
+
+* `Array`: A list of node keys.
+
 ### Properties
 
 | Property             | Type     | Description                                                                                                            | Default     |

src/index.js

@@ -1,2 +1,7 @@
-// Export default to provide support for non-ES6 solutions
-module.exports = require('./js/CheckboxTree').default;
+const tree = require('./js/CheckboxTree').default;
+const utils = require('./js/utils');
+
+module.exports = {
+    default: tree,
+    ...utils,
+};

src/js/utils.js

@@ -0,0 +1,27 @@
+/**
+ * @param {Array} nodes The nodes to traverse.
+ * @param {number} targetLevel How deep to expand the nodes.
+ * @param {int} currentLevel The current level in the recursive chain.
+ *
+ * @returns {Array}
+ */
+function expandNodesToLevel(nodes, targetLevel, currentLevel = 0) {
+    if (currentLevel > targetLevel) {
+        return [];
+    }
+
+    let expanded = [];
+    nodes.forEach((node) => {
+        if (node.children) {
+            expanded = [
+                ...expanded,
+                node.value,
+                ...expandNodesToLevel(node.children, targetLevel, currentLevel + 1),
+            ];
+        }
+    });
+    return expanded;
+}
+
+// eslint-disable-next-line import/prefer-default-export
+export { expandNodesToLevel };

test/.eslintrc

@@ -3,6 +3,7 @@
     "mocha": true
   },
   "rules": {
+    "import/no-extraneous-dependencies": ["error", {"devDependencies": ["**/*.js"]}],
     "react/jsx-props-no-spreading": "off"
   }
 }

test/utils.js

@@ -0,0 +1,46 @@
+import { assert } from 'chai';
+
+import { expandNodesToLevel } from '../src';
+
+const nestedTree = [{
+    value: '0',
+    label: 'Node 0',
+    children: [{
+        value: '0-0',
+        label: 'Node 0-0',
+    }, {
+        value: '0-1',
+        label: 'Node 0-1',
+        children: [{
+            value: '0-1-0',
+            label: 'Node 0-1-0',
+            children: [{
+                value: '0-1-0-0',
+                label: 'Node 0-1-0-0',
+            }],
+        }, {
+            value: '0-1-1',
+            label: 'Node 0-1-1',
+            children: [{
+                value: '0-1-1-0',
+                label: 'Node 0-1-1-0',
+            }],
+        }],
+    }, {
+        value: '0-2',
+        label: 'Node 0-2',
+    }],
+}, {
+    value: '1',
+    label: 'Node 1',
+}];
+
+describe('utils', () => {
+    describe('expandNodesToLevel', () => {
+        it('should recursively traverse a tree of nodes and return the key values of parents from the level specified', () => {
+            const expected = ['0', '0-1'];
+
+            assert.equal(expected, expandNodesToLevel(nestedTree, 1));
+        });
+    });
+});