JavaScript Navigator getVRDisplays() Method

const lines = [
  "getVRDisplays: " +
    (typeof navigator.getVRDisplays === "function" ? "available" : "missing"),
  "activeVRDisplays: " +
    ("activeVRDisplays" in navigator ? "available" : "missing"),
  "navigator.xr: " + ("xr" in navigator ? "available" : "missing")
];
console.log(lines.join("\n"));

async function listVrDisplays() {
  if (typeof navigator.getVRDisplays !== "function") {
    return "getVRDisplays not supported";
  }
  try {
    const displays = await navigator.getVRDisplays();
    return "VR displays found: " + displays.length;
  } catch (err) {
    return "Error: " + err.name;
  }
}

listVrDisplays().then(console.log);

async function inspectVrDisplays() {
  if (typeof navigator.getVRDisplays !== "function") {
    return "API missing";
  }
  const displays = await navigator.getVRDisplays();
  if (!displays.length) return "No VR displays";
  return displays
    .map((d, i) => {
      return (
        "#" + i +
        " id=" + d.displayId +
        " name=" + (d.displayName || "n/a") +
        " presenting=" + !!d.isPresenting
      );
    })
    .join("\n");
}

inspectVrDisplays().then(console.log).catch((err) => {
  console.log("Error: " + err.name);
});

async function compareVrApis() {
  const result = {
    getVRDisplays: "missing",
    availableCount: null,
    activeVRDisplays: "missing",
    presentingCount: null
  };

  if (typeof navigator.getVRDisplays === "function") {
    result.getVRDisplays = "available";
    try {
      const displays = await navigator.getVRDisplays();
      result.availableCount = displays.length;
    } catch (err) {
      result.availableCount = "error:" + err.name;
    }
  }

  if ("activeVRDisplays" in navigator) {
    result.activeVRDisplays = "available";
    result.presentingCount = navigator.activeVRDisplays.length;
  }

  return JSON.stringify(result);
}

compareVrApis().then(console.log);

async function preferWebXr() {
  if (!navigator.xr) {
    return {
      ok: false,
      reason: "no-navigator-xr",
      tip: "Use A-Frame / Three.js / Babylon.js or a 2D fallback"
    };
  }
  try {
    const immersiveVr = await navigator.xr.isSessionSupported("immersive-vr");
    return {
      ok: true,
      reason: "webxr",
      immersiveVr: immersiveVr,
      tip: "Call requestSession after a user gesture when ready"
    };
  } catch (err) {
    return { ok: false, reason: err.name };
  }
}

preferWebXr().then((result) => console.log(JSON.stringify(result)));