Added method for computing content nodes positions and getting text from range

src/__tests__/index.test.ts

@@ -0,0 +1,48 @@
+/**
+ * @jest-environment jsdom
+ */
+
+import { CacheInterface, HTMLPagination } from "../index";
+
+describe("HTMLPagination", () => {
+  let hp: HTMLPagination;
+
+  const content = document.createElement("div");
+  const container = document.createElement("div");
+  class Cache extends CacheInterface {
+    g(key: string) {
+      return localStorage.getItem(key);
+    }
+    s(key: string, value: string) {
+      localStorage.setItem(key, value);
+    }
+  }
+
+  beforeEach(() => {
+    content.innerHTML = "";
+    content.innerHTML = "<div><p>aa</p><p>bb<span>cc</span>dd</p></div>";
+
+    container.innerHTML = "";
+
+    hp = new HTMLPagination(content, container, new Cache());
+  });
+
+  test("Computes positions for each text node", () => {
+    expect(hp.elementPositions.map((el) => el[0])).toEqual([0, 2, 4, 6]);
+  });
+
+  test("Gets element by position", () => {
+    expect(hp.getElementForPosition(0)[0]).toBe(0);
+    expect(hp.getElementForPosition(1)[0]).toBe(0);
+    expect(hp.getElementForPosition(2)[0]).toBe(2);
+    expect(hp.getElementForPosition(3)[0]).toBe(2);
+  });
+
+  test("Gets html content for range of text", () => {
+    expect(hp.getFromRange(0, 8)).toEqual(
+      "<p>aa</p><p>bb<span>cc</span>dd</p>"
+    );
+    expect(hp.getFromRange(0, 3)).toEqual("<p>aa</p><p>b</p>");
+    expect(hp.getFromRange(5, 7)).toEqual("<span>c</span>d");
+  });
+});