feat: add "subgraph" method (#70)

docs/object-graph.doc.md

@@ -48,6 +48,16 @@ Returns a node of the object graph.
 
 Returns a copy of the original object graph.
 
+### subgraph()
+
+Returns a subgraph of the original object graph.
+
+#### Parameters
+
+| Name | Type | Default | Description |
+| --- | --- | --- | --- |
+| nodeKeys | `Array<string>` | - | __Required.__ The array of keys of the nodes to add to the object subgraph. |
+
 ### add()
 
 Adds a node to the object graph.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@kasnix/structured-objects",
-  "version": "1.2.2",
+  "version": "1.3.0",
   "repository": {
     "type": "git",
     "url": "git+https://github.com/luckasnix/structured-objects.git"

src/object-graph.ts

@@ -81,6 +81,20 @@ export class ObjectGraph<NodeValue extends Record<string, unknown>> {
     return new ObjectGraph(Array.from(this.nodes.values()), this.keyExtractor);
   }
 
+  /**
+   * @description Returns a subgraph of the original object graph.
+   * @since 1.3.0
+   */
+  public subgraph(nodeKeys: Array<string>): ObjectGraph<NodeValue> {
+    const subgraph = new ObjectGraph([], this.keyExtractor);
+    for (const [nodeKey, nodeValue] of this.nodes) {
+      if (nodeKeys.includes(nodeKey)) {
+        subgraph.add(nodeValue);
+      }
+    }
+    return subgraph;
+  }
+
   /**
    * @description Adds a node to the object graph.
    * @since 1.0.0

tests/object-graph.test.ts

@@ -90,6 +90,16 @@ describe("copy()", () => {
   });
 });
 
+describe("subgraph()", () => {
+  test("gets a subgraph of the original object graph", () => {
+    const shirtsObjectGraph = new ObjectGraph<Shirt>(shirtsMock, (shirt) => shirt.sku);
+    const shirtsObjectSubgraph = shirtsObjectGraph.subgraph(["1", "2", "3", "4"]);
+
+    expect(shirtsObjectGraph).toHaveLength(8);
+    expect(shirtsObjectSubgraph).toHaveLength(4);
+  });
+});
+
 describe("add()", () => {
   test("logs an error when a node with the same key already exists in the object graph", () => {
     const consoleErrorSpy = vi.spyOn(console, "error");