diff --git a/js/adapters.ts b/js/adapters.ts
index 352cfa9..f829370 100644
--- a/js/adapters.ts
+++ b/js/adapters.ts
@@ -17,17 +17,17 @@ export const leafletRasterLayer = (source: PMTiles, options: any) => {
       };
       if (!loaded) {
         source.getHeader().then((header) => {
-          if (header.tileType == TileType.Mvt) {
+          if (header.tileType === TileType.Mvt) {
             console.error(
               "Error: archive contains MVT vector tiles, but leafletRasterLayer is for displaying raster tiles. See https://github.com/protomaps/PMTiles/tree/main/js for details."
             );
-          } else if (header.tileType == 2) {
+          } else if (header.tileType === 2) {
             mimeType = "image/png";
-          } else if (header.tileType == 3) {
+          } else if (header.tileType === 3) {
             mimeType = "image/jpeg";
-          } else if (header.tileType == 4) {
+          } else if (header.tileType === 4) {
             mimeType = "image/webp";
-          } else if (header.tileType == 5) {
+          } else if (header.tileType === 5) {
             mimeType = "image/avif";
           }
         });
@@ -115,7 +115,7 @@ export class Protocol {
     params: RequestParameters,
     callback: ResponseCallback
   ): Cancelable => {
-    if (params.type == "json") {
+    if (params.type === "json") {
       const pmtilesUrl = params.url.substr(10);
       let instance = this.tiles.get(pmtilesUrl);
       if (!instance) {
@@ -127,7 +127,7 @@ export class Protocol {
         .getHeader()
         .then((h) => {
           const tilejson = {
-            tiles: [params.url + "/{z}/{x}/{y}"],
+            tiles: [`${params.url}/{z}/{x}/{y}`],
             minzoom: h.minZoom,
             maxzoom: h.maxZoom,
             bounds: [h.minLon, h.minLat, h.maxLon, h.maxLat],
@@ -141,60 +141,56 @@ export class Protocol {
       return {
         cancel: () => {},
       };
-    } else {
-      const re = new RegExp(/pmtiles:\/\/(.+)\/(\d+)\/(\d+)\/(\d+)/);
-      const result = params.url.match(re);
-      if (!result) {
-        throw new Error("Invalid PMTiles protocol URL");
-        return {
-          cancel: () => {},
-        };
-      }
-      const pmtilesUrl = result[1];
-
-      let instance = this.tiles.get(pmtilesUrl);
-      if (!instance) {
-        instance = new PMTiles(pmtilesUrl);
-        this.tiles.set(pmtilesUrl, instance);
-      }
-      const z = result[2];
-      const x = result[3];
-      const y = result[4];
-
-      const controller = new AbortController();
-      const signal = controller.signal;
-      const cancel = () => {
-        controller.abort();
-      };
-
-      instance.getHeader().then((header) => {
-        instance!
-          .getZxy(+z, +x, +y, signal)
-          .then((resp) => {
-            if (resp) {
-              callback(
-                null,
-                new Uint8Array(resp.data),
-                resp.cacheControl,
-                resp.expires
-              );
-            } else {
-              if (header.tileType == TileType.Mvt) {
-                callback(null, new Uint8Array(), null, null);
-              } else {
-                callback(null, null, null, null);
-              }
-            }
-          })
-          .catch((e) => {
-            if ((e as Error).name !== "AbortError") {
-              callback(e, null, null, null);
-            }
-          });
-      });
-      return {
-        cancel: cancel,
-      };
     }
+    const re = new RegExp(/pmtiles:\/\/(.+)\/(\d+)\/(\d+)\/(\d+)/);
+    const result = params.url.match(re);
+    if (!result) {
+      throw new Error("Invalid PMTiles protocol URL");
+    }
+    const pmtilesUrl = result[1];
+
+    let instance = this.tiles.get(pmtilesUrl);
+    if (!instance) {
+      instance = new PMTiles(pmtilesUrl);
+      this.tiles.set(pmtilesUrl, instance);
+    }
+    const z = result[2];
+    const x = result[3];
+    const y = result[4];
+
+    const controller = new AbortController();
+    const signal = controller.signal;
+    const cancel = () => {
+      controller.abort();
+    };
+
+    instance.getHeader().then((header) => {
+      instance
+        ?.getZxy(+z, +x, +y, signal)
+        .then((resp) => {
+          if (resp) {
+            callback(
+              null,
+              new Uint8Array(resp.data),
+              resp.cacheControl,
+              resp.expires
+            );
+          } else {
+            if (header.tileType === TileType.Mvt) {
+              callback(null, new Uint8Array(), null, null);
+            } else {
+              callback(null, null, null, null);
+            }
+          }
+        })
+        .catch((e) => {
+          if ((e as Error).name !== "AbortError") {
+            callback(e, null, null, null);
+          }
+        });
+    });
+    return {
+      cancel: cancel,
+    };
   };
 }
diff --git a/js/index.ts b/js/index.ts
index 7901f0b..b8859cb 100644
--- a/js/index.ts
+++ b/js/index.ts
@@ -13,9 +13,8 @@ function toNum(low: number, high: number): number {
 
 function readVarintRemainder(l: number, p: BufferPosition): number {
   const buf = p.buf;
-  let h, b;
-  b = buf[p.pos++];
-  h = (b & 0x70) >> 4;
+  let b = buf[p.pos++];
+  let h = (b & 0x70) >> 4;
   if (b < 0x80) return toNum(l, h);
   b = buf[p.pos++];
   h |= (b & 0x7f) << 3;
@@ -37,10 +36,8 @@ function readVarintRemainder(l: number, p: BufferPosition): number {
 
 export function readVarint(p: BufferPosition): number {
   const buf = p.buf;
-  let val, b;
-
-  b = buf[p.pos++];
-  val = b & 0x7f;
+  let b = buf[p.pos++];
+  let val = b & 0x7f;
   if (b < 0x80) return val;
   b = buf[p.pos++];
   val |= (b & 0x7f) << 7;
@@ -58,8 +55,8 @@ export function readVarint(p: BufferPosition): number {
 }
 
 function rotate(n: number, xy: number[], rx: number, ry: number): void {
-  if (ry == 0) {
-    if (rx == 1) {
+  if (ry === 0) {
+    if (rx === 1) {
       xy[0] = n - 1 - xy[0];
       xy[1] = n - 1 - xy[1];
     }
@@ -70,7 +67,7 @@ function rotate(n: number, xy: number[], rx: number, ry: number): void {
 }
 
 function idOnLevel(z: number, pos: number): [number, number, number] {
-  const n = Math.pow(2, z);
+  const n = 2 ** z;
   let rx = pos;
   let ry = pos;
   let t = pos;
@@ -99,12 +96,12 @@ export function zxyToTileId(z: number, x: number, y: number): number {
   if (z > 26) {
     throw Error("Tile zoom level exceeds max safe number limit (26)");
   }
-  if (x > Math.pow(2, z) - 1 || y > Math.pow(2, z) - 1) {
+  if (x > 2 ** z - 1 || y > 2 ** z - 1) {
     throw Error("tile x/y outside zoom level bounds");
   }
 
   const acc = tzValues[z];
-  const n = Math.pow(2, z);
+  const n = 2 ** z;
   let rx = 0;
   let ry = 0;
   let d = 0;
@@ -161,19 +158,18 @@ async function defaultDecompress(
 ): Promise<ArrayBuffer> {
   if (compression === Compression.None || compression === Compression.Unknown) {
     return buf;
-  } else if (compression === Compression.Gzip) {
-    if (typeof (globalThis as any).DecompressionStream == "undefined") {
-      return decompressSync(new Uint8Array(buf));
-    } else {
-      const stream = new Response(buf).body!;
-      const result: ReadableStream<Uint8Array> = stream.pipeThrough(
-        new (globalThis as any).DecompressionStream("gzip")
-      );
-      return new Response(result).arrayBuffer();
-    }
-  } else {
-    throw Error("Compression method not supported");
   }
+  if (compression === Compression.Gzip) {
+    if (typeof (globalThis as any).DecompressionStream === "undefined") {
+      return decompressSync(new Uint8Array(buf));
+    }
+    const stream = new Response(buf).body!;
+    const result: ReadableStream<Uint8Array> = stream.pipeThrough(
+      new (globalThis as any).DecompressionStream("gzip")
+    );
+    return new Response(result).arrayBuffer();
+  }
+  throw Error("Compression method not supported");
 }
 
 export enum TileType {
@@ -310,10 +306,7 @@ export class FetchSource implements Source {
     }
 
     const requestHeaders = new Headers(this.customHeaders);
-    requestHeaders.set(
-      "Range",
-      "bytes=" + offset + "-" + (offset + length - 1)
-    );
+    requestHeaders.set("Range", `bytes=${offset}-${offset + length - 1}`);
 
     let resp = await fetch(this.url, {
       signal: signal,
@@ -333,12 +326,12 @@ export class FetchSource implements Source {
       const actualLength = +contentRange.substr(8);
       resp = await fetch(this.url, {
         signal: signal,
-        headers: { Range: "bytes=0-" + (actualLength - 1) },
+        headers: { range: `bytes=0-${actualLength - 1}` },
       });
     }
 
     if (resp.status >= 300) {
-      throw Error("Bad response code: " + resp.status);
+      throw Error(`Bad response code: ${resp.status}`);
     }
 
     const contentLength = resp.headers.get("Content-Length");
@@ -365,7 +358,7 @@ export class FetchSource implements Source {
 export function getUint64(v: DataView, offset: number): number {
   const wh = v.getUint32(offset + 4, true);
   const wl = v.getUint32(offset + 0, true);
-  return wh * Math.pow(2, 32) + wl;
+  return wh * 2 ** 32 + wl;
 }
 
 export function bytesToHeader(bytes: ArrayBuffer, etag?: string): Header {
@@ -447,7 +440,8 @@ function detectVersion(a: ArrayBuffer): number {
       "PMTiles spec version 2 has been deprecated; please see github.com/protomaps/PMTiles for tools to upgrade"
     );
     return 2;
-  } else if (v.getUint16(2, true) === 1) {
+  }
+  if (v.getUint16(2, true) === 1) {
     console.warn(
       "PMTiles spec version 1 has been deprecated; please see github.com/protomaps/PMTiles for tools to upgrade"
     );
@@ -496,10 +490,9 @@ async function getHeaderAndRoot(
   const headerData = resp.data.slice(0, HEADER_SIZE_BYTES);
 
   let respEtag = resp.etag;
-  if (currentEtag && resp.etag != currentEtag) {
+  if (currentEtag && resp.etag !== currentEtag) {
     console.warn(
-      "ETag conflict detected; your HTTP server might not support content-based ETag headers. ETags disabled for " +
-        source.getKey()
+      `ETag conflict detected; your HTTP server might not support content-based ETag headers. ETags disabled for ${source.getKey()}`
     );
     respEtag = undefined;
   }
@@ -513,14 +506,9 @@ async function getHeaderAndRoot(
       header.rootDirectoryOffset,
       header.rootDirectoryOffset + header.rootDirectoryLength
     );
-    const dirKey =
-      source.getKey() +
-      "|" +
-      (header.etag || "") +
-      "|" +
-      header.rootDirectoryOffset +
-      "|" +
-      header.rootDirectoryLength;
+    const dirKey = `${source.getKey()}|${header.etag || ""}|${
+      header.rootDirectoryOffset
+    }|${header.rootDirectoryLength}`;
 
     const rootDir = deserializeIndex(
       await decompress(rootDirData, header.internalCompression)
@@ -581,7 +569,7 @@ export class ResolvedValueCache {
     const cacheKey = source.getKey();
     if (this.cache.has(cacheKey)) {
       this.cache.get(cacheKey)!.lastUsed = this.counter++;
-      const data = this.cache.get(cacheKey)!.data;
+      const data = this.cache.get(cacheKey)?.data;
       return data as Header;
     }
 
@@ -612,11 +600,12 @@ export class ResolvedValueCache {
     length: number,
     header: Header
   ): Promise<Entry[]> {
-    const cacheKey =
-      source.getKey() + "|" + (header.etag || "") + "|" + offset + "|" + length;
+    const cacheKey = `${source.getKey()}|${
+      header.etag || ""
+    }|${offset}|${length}`;
     if (this.cache.has(cacheKey)) {
       this.cache.get(cacheKey)!.lastUsed = this.counter++;
-      const data = this.cache.get(cacheKey)!.data;
+      const data = this.cache.get(cacheKey)?.data;
       return data as Entry[];
     }
 
@@ -642,11 +631,12 @@ export class ResolvedValueCache {
     length: number,
     header: Header
   ): Promise<ArrayBuffer> {
-    const cacheKey =
-      source.getKey() + "|" + (header.etag || "") + "|" + offset + "|" + length;
+    const cacheKey = `${source.getKey()}|${
+      header.etag || ""
+    }|${offset}|${length}`;
     if (this.cache.has(cacheKey)) {
       this.cache.get(cacheKey)!.lastUsed = this.counter++;
-      const data = await this.cache.get(cacheKey)!.data;
+      const data = await this.cache.get(cacheKey)?.data;
       return data as ArrayBuffer;
     }
 
@@ -716,7 +706,7 @@ export class SharedPromiseCache {
     const cacheKey = source.getKey();
     if (this.cache.has(cacheKey)) {
       this.cache.get(cacheKey)!.lastUsed = this.counter++;
-      const data = await this.cache.get(cacheKey)!.data;
+      const data = await this.cache.get(cacheKey)?.data;
       return data as Header;
     }
 
@@ -746,11 +736,12 @@ export class SharedPromiseCache {
     length: number,
     header: Header
   ): Promise<Entry[]> {
-    const cacheKey =
-      source.getKey() + "|" + (header.etag || "") + "|" + offset + "|" + length;
+    const cacheKey = `${source.getKey()}|${
+      header.etag || ""
+    }|${offset}|${length}`;
     if (this.cache.has(cacheKey)) {
       this.cache.get(cacheKey)!.lastUsed = this.counter++;
-      const data = await this.cache.get(cacheKey)!.data;
+      const data = await this.cache.get(cacheKey)?.data;
       return data as Entry[];
     }
 
@@ -775,11 +766,12 @@ export class SharedPromiseCache {
     length: number,
     header: Header
   ): Promise<ArrayBuffer> {
-    const cacheKey =
-      source.getKey() + "|" + (header.etag || "") + "|" + offset + "|" + length;
+    const cacheKey = `${source.getKey()}|${
+      header.etag || ""
+    }|${offset}|${length}`;
     if (this.cache.has(cacheKey)) {
       this.cache.get(cacheKey)!.lastUsed = this.counter++;
-      const data = await this.cache.get(cacheKey)!.data;
+      const data = await this.cache.get(cacheKey)?.data;
       return data as ArrayBuffer;
     }
 
@@ -899,10 +891,9 @@ export class PMTiles {
             cacheControl: resp.cacheControl,
             expires: resp.expires,
           };
-        } else {
-          dO = header.leafDirectoryOffset + entry.offset;
-          dL = entry.length;
         }
+        dO = header.leafDirectoryOffset + entry.offset;
+        dL = entry.length;
       } else {
         // TODO: We should in fact return a valid RangeResponse
         // with empty data, but filled in cache control / expires headers
@@ -924,9 +915,8 @@ export class PMTiles {
       if (e instanceof EtagMismatch) {
         this.cache.invalidate(this.source, e.message);
         return await this.getZxyAttempt(z, x, y, signal);
-      } else {
-        throw e;
       }
+      throw e;
     }
   }
 
@@ -955,9 +945,8 @@ export class PMTiles {
       if (e instanceof EtagMismatch) {
         this.cache.invalidate(this.source, e.message);
         return await this.getMetadataAttempt();
-      } else {
-        throw e;
       }
+      throw e;
     }
   }
 }
diff --git a/js/package.json b/js/package.json
index db98239..f9ffdb1 100644
--- a/js/package.json
+++ b/js/package.json
@@ -22,7 +22,8 @@
     "test": "tsx test/index.test.ts",
     "tsc": "tsc --noEmit --watch",
     "prettier": "prettier --write *.ts test/*.ts",
-    "prettier-check": "prettier --check *.ts test/*.ts"
+    "prettier-check": "prettier --check *.ts test/*.ts",
+    "biome": "biome check adapters.ts index.ts v2.ts test"
   },
   "homepage": "https://github.com/protomaps/pmtiles",
   "author": "Brandon Liu",
diff --git a/js/test/v2.test.ts b/js/test/v2.test.ts
index c33e1c9..1fe92bc 100644
--- a/js/test/v2.test.ts
+++ b/js/test/v2.test.ts
@@ -14,22 +14,22 @@ import {
 test("stub data", () => {
   const dataview = new DataView(
     createDirectory([
-      { z: 5, x: 1000, y: 2000, offset: 1000, length: 2000, is_dir: false },
+      { z: 5, x: 1000, y: 2000, offset: 1000, length: 2000, isDir: false },
       {
         z: 14,
         x: 16383,
         y: 16383,
         offset: 999999,
         length: 999,
-        is_dir: false,
+        isDir: false,
       },
     ])
   );
-  var zRaw = dataview.getUint8(17 + 0);
-  var x = getUint24(dataview, 17 + 1);
-  var y = getUint24(dataview, 17 + 4);
-  var offset = getUint48(dataview, 17 + 7);
-  var length = dataview.getUint32(17 + 13, true);
+  const zRaw = dataview.getUint8(17 + 0);
+  const x = getUint24(dataview, 17 + 1);
+  const y = getUint24(dataview, 17 + 4);
+  const offset = getUint48(dataview, 17 + 7);
+  const length = dataview.getUint32(17 + 13, true);
   assert.strictEqual(zRaw, 14);
   assert.strictEqual(x, 16383);
   assert.strictEqual(y, 16383);
@@ -38,24 +38,24 @@ test("stub data", () => {
 test("get entry", () => {
   const view = new DataView(
     createDirectory([
-      { z: 5, x: 1000, y: 2000, offset: 1000, length: 2000, is_dir: false },
+      { z: 5, x: 1000, y: 2000, offset: 1000, length: 2000, isDir: false },
       {
         z: 14,
         x: 16383,
         y: 16383,
         offset: 999999,
         length: 999,
-        is_dir: false,
+        isDir: false,
       },
     ])
   );
   const entry = queryTile(view, 14, 16383, 16383);
-  assert.strictEqual(entry!.z, 14);
-  assert.strictEqual(entry!.x, 16383);
-  assert.strictEqual(entry!.y, 16383);
-  assert.strictEqual(entry!.offset, 999999);
-  assert.strictEqual(entry!.length, 999);
-  assert.strictEqual(entry!.is_dir, false);
+  assert.strictEqual(entry?.z, 14);
+  assert.strictEqual(entry?.x, 16383);
+  assert.strictEqual(entry?.y, 16383);
+  assert.strictEqual(entry?.offset, 999999);
+  assert.strictEqual(entry?.length, 999);
+  assert.strictEqual(entry?.isDir, false);
   assert.strictEqual(queryLeafdir(view, 14, 16383, 16383), null);
 });
 
@@ -68,17 +68,17 @@ test("get leafdir", () => {
         y: 16383,
         offset: 999999,
         length: 999,
-        is_dir: true,
+        isDir: true,
       },
     ])
   );
   const entry = queryLeafdir(view, 14, 16383, 16383);
-  assert.strictEqual(entry!.z, 14);
-  assert.strictEqual(entry!.x, 16383);
-  assert.strictEqual(entry!.y, 16383);
-  assert.strictEqual(entry!.offset, 999999);
-  assert.strictEqual(entry!.length, 999);
-  assert.strictEqual(entry!.is_dir, true);
+  assert.strictEqual(entry?.z, 14);
+  assert.strictEqual(entry?.x, 16383);
+  assert.strictEqual(entry?.y, 16383);
+  assert.strictEqual(entry?.offset, 999999);
+  assert.strictEqual(entry?.length, 999);
+  assert.strictEqual(entry?.isDir, true);
   assert.strictEqual(queryTile(view, 14, 16383, 16383), null);
 });
 
@@ -91,14 +91,14 @@ test("derive the leaf level", () => {
         y: 3,
         offset: 0,
         length: 0,
-        is_dir: true,
+        isDir: true,
       },
     ])
   );
   let leaf = deriveLeaf(view, { z: 7, x: 6, y: 6 });
-  assert.strictEqual(leaf!.z, 6);
-  assert.strictEqual(leaf!.x, 3);
-  assert.strictEqual(leaf!.y, 3);
+  assert.strictEqual(leaf?.z, 6);
+  assert.strictEqual(leaf?.x, 3);
+  assert.strictEqual(leaf?.y, 3);
   view = new DataView(
     createDirectory([
       {
@@ -107,7 +107,7 @@ test("derive the leaf level", () => {
         y: 3,
         offset: 0,
         length: 0,
-        is_dir: false,
+        isDir: false,
       },
     ])
   );
@@ -124,7 +124,7 @@ test("convert spec v1 directory to spec v2 directory", () => {
         y: 3,
         offset: 3,
         length: 3,
-        is_dir: true,
+        isDir: true,
       },
       {
         z: 6,
@@ -132,7 +132,7 @@ test("convert spec v1 directory to spec v2 directory", () => {
         y: 2,
         offset: 2,
         length: 2,
-        is_dir: false,
+        isDir: false,
       },
       {
         z: 6,
@@ -140,21 +140,21 @@ test("convert spec v1 directory to spec v2 directory", () => {
         y: 1,
         offset: 1,
         length: 1,
-        is_dir: false,
+        isDir: false,
       },
     ])
   );
   let entry = queryLeafdir(view, 7, 3, 3);
-  assert.strictEqual(entry!.offset, 3);
+  assert.strictEqual(entry?.offset, 3);
   entry = queryTile(view, 6, 2, 2);
-  assert.strictEqual(entry!.offset, 2);
+  assert.strictEqual(entry?.offset, 2);
   entry = queryTile(view, 6, 2, 1);
-  assert.strictEqual(entry!.offset, 1);
+  assert.strictEqual(entry?.offset, 1);
 
   entry = parseEntry(view, 0);
-  assert.strictEqual(entry!.offset, 1);
+  assert.strictEqual(entry?.offset, 1);
   entry = parseEntry(view, 1);
-  assert.strictEqual(entry!.offset, 2);
+  assert.strictEqual(entry?.offset, 2);
   entry = parseEntry(view, 2);
-  assert.strictEqual(entry!.offset, 3);
+  assert.strictEqual(entry?.offset, 3);
 });
diff --git a/js/test/v3.test.ts b/js/test/v3.test.ts
index 51592e6..3e7bae5 100644
--- a/js/test/v3.test.ts
+++ b/js/test/v3.test.ts
@@ -64,8 +64,8 @@ test("a lot of tiles", () => {
 });
 
 test("tile extremes", () => {
-  for (var z = 0; z < 27; z++) {
-    const dim = Math.pow(2, z) - 1;
+  for (let z = 0; z < 27; z++) {
+    const dim = 2 ** z - 1;
     const tl = tileIdToZxy(zxyToTileId(z, 0, 0));
     assert.deepEqual([z, 0, 0], tl);
     const tr = tileIdToZxy(zxyToTileId(z, dim, 0));
@@ -100,9 +100,9 @@ test("tile search for first entry == id", () => {
   const entries: Entry[] = [
     { tileId: 100, offset: 1, length: 1, runLength: 1 },
   ];
-  const entry = findTile(entries, 100)!;
-  assert.strictEqual(entry.offset, 1);
-  assert.strictEqual(entry.length, 1);
+  const entry = findTile(entries, 100);
+  assert.strictEqual(entry?.offset, 1);
+  assert.strictEqual(entry?.length, 1);
   assert.strictEqual(findTile(entries, 101), null);
 });
 
@@ -111,32 +111,32 @@ test("tile search with runlength", () => {
     { tileId: 3, offset: 3, length: 1, runLength: 2 },
     { tileId: 5, offset: 5, length: 1, runLength: 2 },
   ];
-  const entry = findTile(entries, 4)!;
-  assert.strictEqual(entry.offset, 3);
+  const entry = findTile(entries, 4);
+  assert.strictEqual(entry?.offset, 3);
 });
 
 test("tile search with multiple tile entries", () => {
   let entries: Entry[] = [{ tileId: 100, offset: 1, length: 1, runLength: 2 }];
-  let entry = findTile(entries, 101)!;
-  assert.strictEqual(entry.offset, 1);
-  assert.strictEqual(entry.length, 1);
+  let entry = findTile(entries, 101);
+  assert.strictEqual(entry?.offset, 1);
+  assert.strictEqual(entry?.length, 1);
 
   entries = [
     { tileId: 100, offset: 1, length: 1, runLength: 1 },
     { tileId: 150, offset: 2, length: 2, runLength: 2 },
   ];
-  entry = findTile(entries, 151)!;
-  assert.strictEqual(entry.offset, 2);
-  assert.strictEqual(entry.length, 2);
+  entry = findTile(entries, 151);
+  assert.strictEqual(entry?.offset, 2);
+  assert.strictEqual(entry?.length, 2);
 
   entries = [
     { tileId: 50, offset: 1, length: 1, runLength: 2 },
     { tileId: 100, offset: 2, length: 2, runLength: 1 },
     { tileId: 150, offset: 3, length: 3, runLength: 1 },
   ];
-  entry = findTile(entries, 51)!;
-  assert.strictEqual(entry.offset, 1);
-  assert.strictEqual(entry.length, 1);
+  entry = findTile(entries, 51);
+  assert.strictEqual(entry?.offset, 1);
+  assert.strictEqual(entry?.length, 1);
 });
 
 test("leaf search", () => {
@@ -144,8 +144,8 @@ test("leaf search", () => {
     { tileId: 100, offset: 1, length: 1, runLength: 0 },
   ];
   const entry = findTile(entries, 150);
-  assert.strictEqual(entry!.offset, 1);
-  assert.strictEqual(entry!.length, 1);
+  assert.strictEqual(entry?.offset, 1);
+  assert.strictEqual(entry?.length, 1);
 });
 
 // inefficient method only for testing
diff --git a/js/v2.ts b/js/v2.ts
index bc66720..2ce7154 100644
--- a/js/v2.ts
+++ b/js/v2.ts
@@ -9,11 +9,11 @@ import {
 } from "./index";
 
 export const shift = (n: number, shift: number) => {
-  return n * Math.pow(2, shift);
+  return n * 2 ** shift;
 };
 
 export const unshift = (n: number, shift: number) => {
-  return Math.floor(n / Math.pow(2, shift));
+  return Math.floor(n / 2 ** shift);
 };
 
 export const getUint24 = (view: DataView, pos: number) => {
@@ -36,7 +36,7 @@ export interface EntryV2 {
   y: number;
   offset: number;
   length: number;
-  is_dir: boolean;
+  isDir: boolean;
 }
 
 const compare = (
@@ -46,11 +46,11 @@ const compare = (
   view: DataView,
   i: number
 ) => {
-  if (tz != view.getUint8(i)) return tz - view.getUint8(i);
+  if (tz !== view.getUint8(i)) return tz - view.getUint8(i);
   const x = getUint24(view, i + 1);
-  if (tx != x) return tx - x;
+  if (tx !== x) return tx - x;
   const y = getUint24(view, i + 4);
-  if (ty != y) return ty - y;
+  if (ty !== y) return ty - y;
   return 0;
 };
 
@@ -68,7 +68,7 @@ export const queryLeafdir = (
       y: y,
       offset: offsetLen[0],
       length: offsetLen[1],
-      is_dir: true,
+      isDir: true,
     };
   }
   return null;
@@ -83,7 +83,7 @@ export const queryTile = (view: DataView, z: number, x: number, y: number) => {
       y: y,
       offset: offsetLen[0],
       length: offsetLen[1],
-      is_dir: false,
+      isDir: false,
     };
   }
   return null;
@@ -112,10 +112,10 @@ const queryView = (
 };
 
 const entrySort = (a: EntryV2, b: EntryV2): number => {
-  if (a.is_dir && !b.is_dir) {
+  if (a.isDir && !b.isDir) {
     return 1;
   }
-  if (!a.is_dir && b.is_dir) {
+  if (!a.isDir && b.isDir) {
     return -1;
   }
   if (a.z !== b.z) {
@@ -136,7 +136,7 @@ export const parseEntry = (dataview: DataView, i: number): EntryV2 => {
     y: getUint24(dataview, i * 17 + 4),
     offset: getUint48(dataview, i * 17 + 7),
     length: dataview.getUint32(i * 17 + 13, true),
-    is_dir: zRaw >> 7 === 1,
+    isDir: zRaw >> 7 === 1,
   };
 };
 
@@ -157,7 +157,7 @@ export const createDirectory = (entries: EntryV2[]): ArrayBuffer => {
   for (let i = 0; i < entries.length; i++) {
     const entry = entries[i];
     let z = entry.z;
-    if (entry.is_dir) z = z | 0x80;
+    if (entry.isDir) z = z | 0x80;
     arr[i * 17] = z;
 
     arr[i * 17 + 1] = entry.x & 0xff;
@@ -187,7 +187,7 @@ export const deriveLeaf = (view: DataView, tile: Zxy): Zxy | null => {
   if (view.byteLength < 17) return null;
   const numEntries = view.byteLength / 17;
   const entry = parseEntry(view, numEntries - 1);
-  if (entry.is_dir) {
+  if (entry.isDir) {
     const leafLevel = entry.z;
     const levelDiff = tile.z - leafLevel;
     const leafX = Math.trunc(tile.x / (1 << levelDiff));
@@ -303,7 +303,7 @@ async function getZxy(
     let tileData = resp.data;
 
     const view = new DataView(tileData);
-    if (view.getUint8(0) == 0x1f && view.getUint8(1) == 0x8b) {
+    if (view.getUint8(0) === 0x1f && view.getUint8(1) === 0x8b) {
       tileData = decompressSync(new Uint8Array(tileData));
     }
 
@@ -341,7 +341,7 @@ async function getZxy(
         let tileData = resp.data;
 
         const view = new DataView(tileData);
-        if (view.getUint8(0) == 0x1f && view.getUint8(1) == 0x8b) {
+        if (view.getUint8(0) === 0x1f && view.getUint8(1) === 0x8b) {
           tileData = decompressSync(new Uint8Array(tileData));
         }
         return {