diff --git a/src/core/murmurhash3.js b/src/core/murmurhash3.js
index f20cdb160..87543ec1f 100644
--- a/src/core/murmurhash3.js
+++ b/src/core/murmurhash3.js
@@ -16,88 +16,85 @@
  * Based on https://code.google.com/p/smhasher/wiki/MurmurHash3.
  * Hashes roughly 100 KB per millisecond on i7 3.4 GHz.
  */
+/* eslint no-var: error */
 
 import { isArrayBuffer, isString } from '../shared/util';
 
-var MurmurHash3_64 = (function MurmurHash3_64Closure(seed) {
-  // Workaround for missing math precision in JS.
-  var MASK_HIGH = 0xffff0000;
-  var MASK_LOW = 0xffff;
+const SEED = 0xc3d2e1f0;
+// Workaround for missing math precision in JS.
+const MASK_HIGH = 0xffff0000;
+const MASK_LOW = 0xffff;
 
-  function MurmurHash3_64(seed) {
-    var SEED = 0xc3d2e1f0;
+class MurmurHash3_64 {
+  constructor(seed) {
     this.h1 = seed ? seed & 0xffffffff : SEED;
     this.h2 = seed ? seed & 0xffffffff : SEED;
   }
 
-  MurmurHash3_64.prototype = {
-    update: function MurmurHash3_64_update(input) {
-      let data, length;
-      if (isString(input)) {
-        data = new Uint8Array(input.length * 2);
-        length = 0;
-        for (let i = 0, ii = input.length; i < ii; i++) {
-          var code = input.charCodeAt(i);
-          if (code <= 0xff) {
-            data[length++] = code;
-          } else {
-            data[length++] = code >>> 8;
-            data[length++] = code & 0xff;
-          }
-        }
-      } else if (isArrayBuffer(input)) {
-        data = input;
-        length = data.byteLength;
-      } else {
-        throw new Error('Wrong data format in MurmurHash3_64_update. ' +
-                        'Input must be a string or array.');
-      }
-
-      var blockCounts = length >> 2;
-      var tailLength = length - blockCounts * 4;
-      // we don't care about endianness here
-      var dataUint32 = new Uint32Array(data.buffer, 0, blockCounts);
-      var k1 = 0;
-      var k2 = 0;
-      var h1 = this.h1;
-      var h2 = this.h2;
-      var C1 = 0xcc9e2d51;
-      var C2 = 0x1b873593;
-      var C1_LOW = C1 & MASK_LOW;
-      var C2_LOW = C2 & MASK_LOW;
-
-      for (let i = 0; i < blockCounts; i++) {
-        if (i & 1) {
-          k1 = dataUint32[i];
-          k1 = (k1 * C1 & MASK_HIGH) | (k1 * C1_LOW & MASK_LOW);
-          k1 = k1 << 15 | k1 >>> 17;
-          k1 = (k1 * C2 & MASK_HIGH) | (k1 * C2_LOW & MASK_LOW);
-          h1 ^= k1;
-          h1 = h1 << 13 | h1 >>> 19;
-          h1 = h1 * 5 + 0xe6546b64;
+  update(input) {
+    let data, length;
+    if (isString(input)) {
+      data = new Uint8Array(input.length * 2);
+      length = 0;
+      for (let i = 0, ii = input.length; i < ii; i++) {
+        const code = input.charCodeAt(i);
+        if (code <= 0xff) {
+          data[length++] = code;
         } else {
-          k2 = dataUint32[i];
-          k2 = (k2 * C1 & MASK_HIGH) | (k2 * C1_LOW & MASK_LOW);
-          k2 = k2 << 15 | k2 >>> 17;
-          k2 = (k2 * C2 & MASK_HIGH) | (k2 * C2_LOW & MASK_LOW);
-          h2 ^= k2;
-          h2 = h2 << 13 | h2 >>> 19;
-          h2 = h2 * 5 + 0xe6546b64;
+          data[length++] = code >>> 8;
+          data[length++] = code & 0xff;
         }
       }
+    } else if (isArrayBuffer(input)) {
+      data = input;
+      length = data.byteLength;
+    } else {
+      throw new Error('Wrong data format in MurmurHash3_64_update. ' +
+                      'Input must be a string or array.');
+    }
 
-      k1 = 0;
+    const blockCounts = length >> 2;
+    const tailLength = length - blockCounts * 4;
+    // We don't care about endianness here.
+    const dataUint32 = new Uint32Array(data.buffer, 0, blockCounts);
+    let k1 = 0, k2 = 0;
+    let h1 = this.h1, h2 = this.h2;
+    const C1 = 0xcc9e2d51, C2 = 0x1b873593;
+    const C1_LOW = C1 & MASK_LOW, C2_LOW = C2 & MASK_LOW;
+
+    for (let i = 0; i < blockCounts; i++) {
+      if (i & 1) {
+        k1 = dataUint32[i];
+        k1 = (k1 * C1 & MASK_HIGH) | (k1 * C1_LOW & MASK_LOW);
+        k1 = k1 << 15 | k1 >>> 17;
+        k1 = (k1 * C2 & MASK_HIGH) | (k1 * C2_LOW & MASK_LOW);
+        h1 ^= k1;
+        h1 = h1 << 13 | h1 >>> 19;
+        h1 = h1 * 5 + 0xe6546b64;
+      } else {
+        k2 = dataUint32[i];
+        k2 = (k2 * C1 & MASK_HIGH) | (k2 * C1_LOW & MASK_LOW);
+        k2 = k2 << 15 | k2 >>> 17;
+        k2 = (k2 * C2 & MASK_HIGH) | (k2 * C2_LOW & MASK_LOW);
+        h2 ^= k2;
+        h2 = h2 << 13 | h2 >>> 19;
+        h2 = h2 * 5 + 0xe6546b64;
+      }
+    }
+
+    k1 = 0;
+
+    switch (tailLength) {
+      case 3:
+        k1 ^= data[blockCounts * 4 + 2] << 16;
+        /* falls through */
+      case 2:
+        k1 ^= data[blockCounts * 4 + 1] << 8;
+        /* falls through */
+      case 1:
+        k1 ^= data[blockCounts * 4];
+        /* falls through */
 
-      switch (tailLength) {
-        case 3:
-          k1 ^= data[blockCounts * 4 + 2] << 16;
-          /* falls through */
-        case 2:
-          k1 ^= data[blockCounts * 4 + 1] << 8;
-          /* falls through */
-        case 1:
-          k1 ^= data[blockCounts * 4];
-          /* falls through */
         k1 = (k1 * C1 & MASK_HIGH) | (k1 * C1_LOW & MASK_LOW);
         k1 = k1 << 15 | k1 >>> 17;
         k1 = (k1 * C2 & MASK_HIGH) | (k1 * C2_LOW & MASK_LOW);
@@ -106,41 +103,29 @@ var MurmurHash3_64 = (function MurmurHash3_64Closure(seed) {
         } else {
           h2 ^= k1;
         }
-      }
+    }
 
-      this.h1 = h1;
-      this.h2 = h2;
-      return this;
-    },
+    this.h1 = h1;
+    this.h2 = h2;
+  }
 
-    hexdigest: function MurmurHash3_64_hexdigest() {
-      var h1 = this.h1;
-      var h2 = this.h2;
+  hexdigest() {
+    let h1 = this.h1, h2 = this.h2;
 
-      h1 ^= h2 >>> 1;
-      h1 = (h1 * 0xed558ccd & MASK_HIGH) | (h1 * 0x8ccd & MASK_LOW);
-      h2 = (h2 * 0xff51afd7 & MASK_HIGH) |
-           (((h2 << 16 | h1 >>> 16) * 0xafd7ed55 & MASK_HIGH) >>> 16);
-      h1 ^= h2 >>> 1;
-      h1 = (h1 * 0x1a85ec53 & MASK_HIGH) | (h1 * 0xec53 & MASK_LOW);
-      h2 = (h2 * 0xc4ceb9fe & MASK_HIGH) |
-           (((h2 << 16 | h1 >>> 16) * 0xb9fe1a85 & MASK_HIGH) >>> 16);
-      h1 ^= h2 >>> 1;
+    h1 ^= h2 >>> 1;
+    h1 = (h1 * 0xed558ccd & MASK_HIGH) | (h1 * 0x8ccd & MASK_LOW);
+    h2 = (h2 * 0xff51afd7 & MASK_HIGH) |
+         (((h2 << 16 | h1 >>> 16) * 0xafd7ed55 & MASK_HIGH) >>> 16);
+    h1 ^= h2 >>> 1;
+    h1 = (h1 * 0x1a85ec53 & MASK_HIGH) | (h1 * 0xec53 & MASK_LOW);
+    h2 = (h2 * 0xc4ceb9fe & MASK_HIGH) |
+         (((h2 << 16 | h1 >>> 16) * 0xb9fe1a85 & MASK_HIGH) >>> 16);
+    h1 ^= h2 >>> 1;
 
-      for (var i = 0, arr = [h1, h2], str = ''; i < arr.length; i++) {
-        var hex = (arr[i] >>> 0).toString(16);
-        while (hex.length < 8) {
-          hex = '0' + hex;
-        }
-        str += hex;
-      }
-
-      return str;
-    },
-  };
-
-  return MurmurHash3_64;
-})();
+    const hex1 = (h1 >>> 0).toString(16), hex2 = (h2 >>> 0).toString(16);
+    return hex1.padStart(8, '0') + hex2.padStart(8, '0');
+  }
+}
 
 export {
   MurmurHash3_64,