diff --git a/js/common.js b/js/common.js
index f0482ae6..d0c53aa5 100644
--- a/js/common.js
+++ b/js/common.js
@@ -11,7 +11,7 @@ global.WebCrypto = require('node-webcrypto-ossl');
 // application libraries to test
 global.$ = global.jQuery = require('./jquery-3.3.1');
 global.RawDeflate = require('./rawinflate-0.3').RawDeflate;
-require('./zlib-1.2.11');
+global.zlib = require('./zlib-1.2.11').zlib;
 require('./prettify');
 global.prettyPrint = window.PR.prettyPrint;
 global.prettyPrintOne = window.PR.prettyPrintOne;
diff --git a/js/zlib-1.2.11.js b/js/zlib-1.2.11.js
index 28752079..ed0abea8 100644
--- a/js/zlib-1.2.11.js
+++ b/js/zlib-1.2.11.js
@@ -1,144 +1,146 @@
 'use strict';
 
-let ret;
+(function() {
+    let ret;
 
-async function initialize() {
-  if (ret) return ret;
+    async function initialize() {
+        if (ret) return ret;
 
-  const COMPRESSION_LEVEL = 7;
-  const NO_ZLIB_HEADER = -1;
-  const CHUNK_SIZE = 32 * 1024;
-  const map = {};
-  const memory = new WebAssembly.Memory({
-    initial: 1,
-    maximum: 1024, // 64MB
-  });
-  const env = {
-    memory,
-    writeToJs(ptr, size) {
-      const o = map[ptr];
-      o.onData(new Uint8Array(memory.buffer, dstPtr, size));
-    },
-    _abort: errno => { console.error(`Error: ${errno}`) },
-    _grow: () => { },
-  };
+        const COMPRESSION_LEVEL = 7;
+        const NO_ZLIB_HEADER = -1;
+        const CHUNK_SIZE = 32 * 1024;
+        const map = {};
+        const memory = new WebAssembly.Memory({
+            initial: 1,
+            maximum: 1024, // 64MB
+        });
+        const env = {
+            memory,
+            writeToJs(ptr, size) {
+                const o = map[ptr];
+                o.onData(new Uint8Array(memory.buffer, dstPtr, size));
+            },
+            _abort: errno => { console.error(`Error: ${errno}`) },
+            _grow: () => { },
+        };
 
-  let ins;
-  if (typeof fetch === 'undefined') {
-    const buff = fs.readFileSync('zlib-1.2.11.wasm');
-    const module = await WebAssembly.compile(buff);
-    ins = await WebAssembly.instantiate(module, { env });
-  } else {
-    ins = await WebAssembly.instantiateStreaming(fetch('zlib-1.2.11.wasm'));
-  }
+        let buff;
+        if (typeof fetch === 'undefined') {
+            buff = fs.readFileSync('zlib-1.2.11.wasm');
+        } else {
+            const resp = await fetch('js/zlib-1.2.11.wasm');
+            buff = await resp.arrayBuffer();
+        }
+        const module = await WebAssembly.compile(buff);
+        const ins = await WebAssembly.instantiate(module, { env });
 
-  const srcPtr = ins.exports._malloc(CHUNK_SIZE);
-  const dstPtr = ins.exports._malloc(CHUNK_SIZE);
+        const srcPtr = ins.exports._malloc(CHUNK_SIZE);
+        const dstPtr = ins.exports._malloc(CHUNK_SIZE);
 
-  class RawDef {
-    constructor() {
-      this.zstreamPtr = ins.exports._createDeflateContext(COMPRESSION_LEVEL, NO_ZLIB_HEADER);
-      map[this.zstreamPtr] = this;
-      this.offset = 0;
-      this.buff = new Uint8Array(CHUNK_SIZE);
+        class RawDef {
+            constructor() {
+                this.zstreamPtr = ins.exports._createDeflateContext(COMPRESSION_LEVEL, NO_ZLIB_HEADER);
+                map[this.zstreamPtr] = this;
+                this.offset = 0;
+                this.buff = new Uint8Array(CHUNK_SIZE);
+            }
+
+            deflate(chunk, flush) {
+                const src = new Uint8Array(memory.buffer, srcPtr, chunk.length);
+                src.set(chunk);
+                ins.exports._deflate(this.zstreamPtr, srcPtr, dstPtr, chunk.length, CHUNK_SIZE, flush);
+            }
+
+            onData(chunk) {
+                if (this.buff.length < this.offset + chunk.length) {
+                    const buff = this.buff;
+                    this.buff = new Uint8Array(this.buff.length * 2);
+                    this.buff.set(buff);
+                }
+                this.buff.set(chunk, this.offset);
+                this.offset += chunk.length;
+            }
+
+            destroy() {
+                ins.exports._freeDeflateContext(this.zstreamPtr);
+                delete map[this.zstreamPtr];
+                this.buff = null;
+            }
+
+            getBuffer() {
+                const res = new Uint8Array(this.offset);
+                for (let i = 0; i < this.offset; ++i) {
+                    res[i] = this.buff[i];
+                }
+                return res;
+            }
+        }
+
+        class RawInf {
+            constructor() {
+                this.zstreamPtr = ins.exports._createInflateContext(NO_ZLIB_HEADER);
+                map[this.zstreamPtr] = this;
+                this.offset = 0;
+                this.buff = new Uint8Array(CHUNK_SIZE);
+            }
+
+            inflate(chunk) {
+                const src = new Uint8Array(memory.buffer, srcPtr, chunk.length);
+                src.set(chunk);
+                ins.exports._inflate(this.zstreamPtr, srcPtr, dstPtr, chunk.length, CHUNK_SIZE);
+            }
+
+            onData(chunk) {
+                if (this.buff.length < this.offset + chunk.length) {
+                    const buff = this.buff;
+                    this.buff = new Uint8Array(this.buff.length * 2);
+                    this.buff.set(buff);
+                }
+                this.buff.set(chunk, this.offset);
+                this.offset += chunk.length;
+            }
+
+            destroy() {
+                ins.exports._freeInflateContext(this.zstreamPtr);
+                delete map[this.zstreamPtr];
+                this.buff = null;
+            }
+
+            getBuffer() {
+                const res = new Uint8Array(this.offset);
+                for (let i = 0; i < this.offset; ++i) {
+                    res[i] = this.buff[i];
+                }
+                return res;
+            }
+        }
+
+        ret = {
+                inflate(rawDeflateBuffer) {
+                    const rawInf = new RawInf();
+                    for (let offset = 0; offset < rawDeflateBuffer.length; offset += CHUNK_SIZE) {
+                        const end = Math.min(offset + CHUNK_SIZE, rawDeflateBuffer.length);
+                        const chunk = rawDeflateBuffer.subarray(offset, end);
+                        rawInf.inflate(chunk);
+                    }
+                    const ret = rawInf.getBuffer();
+                    rawInf.destroy();
+                    return ret;
+                },
+                deflate(rawInflateBuffer) {
+                    const rawDef = new RawDef();
+                    for (let offset = 0; offset < rawInflateBuffer.length; offset += CHUNK_SIZE) {
+                        const end = Math.min(offset + CHUNK_SIZE, rawInflateBuffer.length);
+                        const chunk = rawInflateBuffer.subarray(offset, end);
+                        rawDef.deflate(chunk, rawInflateBuffer.length <= offset + CHUNK_SIZE);
+                    }
+                    const ret = rawDef.getBuffer();
+                    rawDef.destroy();
+                    return ret;
+                },
+        }
+
+        return ret;
     }
-
-    deflate(chunk, flush) {
-      const src = new Uint8Array(memory.buffer, srcPtr, chunk.length);
-      src.set(chunk);
-      ins.exports._deflate(this.zstreamPtr, srcPtr, dstPtr, chunk.length, CHUNK_SIZE, flush);
-    }
-
-    onData(chunk) {
-      if (this.buff.length < this.offset + chunk.length) {
-        const buff = this.buff;
-        this.buff = new Uint8Array(this.buff.length * 2);
-        this.buff.set(buff);
-      }
-      this.buff.set(chunk, this.offset);
-      this.offset += chunk.length;
-    }
-
-    destroy() {
-      ins.exports._freeDeflateContext(this.zstreamPtr);
-      delete map[this.zstreamPtr];
-      this.buff = null;
-    }
-
-    getBuffer() {
-      const res = new Uint8Array(this.offset);
-      for (let i = 0; i < this.offset; ++i) {
-        res[i] = this.buff[i];
-      }
-      return res;
-    }
-  }
-
-  class RawInf {
-    constructor() {
-      this.zstreamPtr = ins.exports._createInflateContext(NO_ZLIB_HEADER);
-      map[this.zstreamPtr] = this;
-      this.offset = 0;
-      this.buff = new Uint8Array(CHUNK_SIZE);
-    }
-
-    inflate(chunk) {
-      const src = new Uint8Array(memory.buffer, srcPtr, chunk.length);
-      src.set(chunk);
-      ins.exports._inflate(this.zstreamPtr, srcPtr, dstPtr, chunk.length, CHUNK_SIZE);
-    }
-
-    onData(chunk) {
-      if (this.buff.length < this.offset + chunk.length) {
-        const buff = this.buff;
-        this.buff = new Uint8Array(this.buff.length * 2);
-        this.buff.set(buff);
-      }
-      this.buff.set(chunk, this.offset);
-      this.offset += chunk.length;
-    }
-
-    destroy() {
-      ins.exports._freeInflateContext(this.zstreamPtr);
-      delete map[this.zstreamPtr];
-      this.buff = null;
-    }
-
-    getBuffer() {
-      const res = new Uint8Array(this.offset);
-      for (let i = 0; i < this.offset; ++i) {
-        res[i] = this.buff[i];
-      }
-      return res;
-    }
-  }
-  
-  ret = {
-    inflate(rawDeflateBuffer) {
-      const rawInf = new RawInf();
-      for (let offset = 0; offset < rawDeflateBuffer.length; offset += CHUNK_SIZE) {
-        const end = Math.min(offset + CHUNK_SIZE, rawDeflateBuffer.length);
-        const chunk = rawDeflateBuffer.subarray(offset, end);
-        rawInf.inflate(chunk);
-      }
-      const ret = rawInf.getBuffer();
-      rawInf.destroy();
-      return ret;
-    },
-    deflate(rawInflateBuffer) {
-      const rawDef = new RawDef();
-      for (let offset = 0; offset < rawInflateBuffer.length; offset += CHUNK_SIZE) {
-        const end = Math.min(offset + CHUNK_SIZE, rawInflateBuffer.length);
-        const chunk = rawInflateBuffer.subarray(offset, end);
-        rawDef.deflate(chunk, rawInflateBuffer.length <= offset + CHUNK_SIZE);
-      }
-      const ret = rawDef.getBuffer();
-      rawDef.destroy();
-      return ret;
-    },
-  }
-
-  return ret;
-}
-
-global.zlib = initialize();
+    this.zlib = initialize();
+}).call(this);