one/dist/esm/link/prefetchViewport.test.js

One is a new React Framework that makes Vite serve both native and web.

import { describe, expect, it, beforeEach, vi } from "vitest";
import { createPrefetchViewport } from "./prefetchViewport";
let mockIOCallback;
const mockObserved = /* @__PURE__ */ new Set();
vi.stubGlobal(
  "IntersectionObserver",
  class {
    constructor(callback) {
      mockIOCallback = callback;
    }
    observe(el) {
      mockObserved.add(el);
    }
    unobserve(el) {
      mockObserved.delete(el);
    }
    disconnect() {
      mockObserved.clear();
    }
  }
);
function simulateIntersect(el, isIntersecting) {
  mockIOCallback(
    [{ target: el, isIntersecting }],
    {}
  );
}
describe("prefetchViewport", () => {
  let prefetched, vp;
  beforeEach(() => {
    prefetched = [], mockObserved.clear(), vp = createPrefetchViewport(), vp.start((href) => prefetched.push(href));
  }), it("prefetches when link enters viewport", () => {
    const el = {};
    vp.observe(el, "/about"), simulateIntersect(el, !0), expect(prefetched).toEqual(["/about"]);
  }), it("does not prefetch when link exits viewport", () => {
    const el = {};
    vp.observe(el, "/about"), simulateIntersect(el, !1), expect(prefetched).toEqual([]);
  }), it("only prefetches each href once", () => {
    const el = {};
    vp.observe(el, "/about"), simulateIntersect(el, !0), simulateIntersect(el, !1), simulateIntersect(el, !0), expect(prefetched).toEqual(["/about"]);
  }), it("cleanup re-enables prefetch for href", () => {
    const el = {}, cleanup = vp.observe(el, "/about");
    simulateIntersect(el, !0), expect(prefetched).toEqual(["/about"]), cleanup(), prefetched.length = 0, vp.observe(el, "/about"), simulateIntersect(el, !0), expect(prefetched).toEqual(["/about"]);
  }), describe("memory and performance", () => {
    it("does not leak elements after cleanup", () => {
      const elements = [], cleanups = [];
      for (let i = 0; i < 100; i++) {
        const el = {};
        elements.push(el), cleanups.push(vp.observe(el, `/page-${i}`));
      }
      expect(vp.nodes.size).toBe(100), cleanups.forEach((c) => c()), expect(vp.nodes.size).toBe(0), expect(vp.done.size).toBe(0);
    }), it("handles rapid observe/unobserve cycles", () => {
      const el = {};
      for (let i = 0; i < 100; i++)
        vp.observe(el, "/test")();
      expect(vp.nodes.size).toBe(0);
    });
  });
});
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