diff --git a/src/core/arithmetic_decoder.js b/src/core/arithmetic_decoder.js
index 446a2c4f8..6d589c8ef 100644
--- a/src/core/arithmetic_decoder.js
+++ b/src/core/arithmetic_decoder.js
@@ -12,8 +12,61 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+/* eslint no-var: error */
 
-/* This class implements the QM Coder decoding as defined in
+// Table C-2
+const QeTable = [
+  { qe: 0x5601, nmps: 1, nlps: 1, switchFlag: 1, },
+  { qe: 0x3401, nmps: 2, nlps: 6, switchFlag: 0, },
+  { qe: 0x1801, nmps: 3, nlps: 9, switchFlag: 0, },
+  { qe: 0x0AC1, nmps: 4, nlps: 12, switchFlag: 0, },
+  { qe: 0x0521, nmps: 5, nlps: 29, switchFlag: 0, },
+  { qe: 0x0221, nmps: 38, nlps: 33, switchFlag: 0, },
+  { qe: 0x5601, nmps: 7, nlps: 6, switchFlag: 1, },
+  { qe: 0x5401, nmps: 8, nlps: 14, switchFlag: 0, },
+  { qe: 0x4801, nmps: 9, nlps: 14, switchFlag: 0, },
+  { qe: 0x3801, nmps: 10, nlps: 14, switchFlag: 0, },
+  { qe: 0x3001, nmps: 11, nlps: 17, switchFlag: 0, },
+  { qe: 0x2401, nmps: 12, nlps: 18, switchFlag: 0, },
+  { qe: 0x1C01, nmps: 13, nlps: 20, switchFlag: 0, },
+  { qe: 0x1601, nmps: 29, nlps: 21, switchFlag: 0, },
+  { qe: 0x5601, nmps: 15, nlps: 14, switchFlag: 1, },
+  { qe: 0x5401, nmps: 16, nlps: 14, switchFlag: 0, },
+  { qe: 0x5101, nmps: 17, nlps: 15, switchFlag: 0, },
+  { qe: 0x4801, nmps: 18, nlps: 16, switchFlag: 0, },
+  { qe: 0x3801, nmps: 19, nlps: 17, switchFlag: 0, },
+  { qe: 0x3401, nmps: 20, nlps: 18, switchFlag: 0, },
+  { qe: 0x3001, nmps: 21, nlps: 19, switchFlag: 0, },
+  { qe: 0x2801, nmps: 22, nlps: 19, switchFlag: 0, },
+  { qe: 0x2401, nmps: 23, nlps: 20, switchFlag: 0, },
+  { qe: 0x2201, nmps: 24, nlps: 21, switchFlag: 0, },
+  { qe: 0x1C01, nmps: 25, nlps: 22, switchFlag: 0, },
+  { qe: 0x1801, nmps: 26, nlps: 23, switchFlag: 0, },
+  { qe: 0x1601, nmps: 27, nlps: 24, switchFlag: 0, },
+  { qe: 0x1401, nmps: 28, nlps: 25, switchFlag: 0, },
+  { qe: 0x1201, nmps: 29, nlps: 26, switchFlag: 0, },
+  { qe: 0x1101, nmps: 30, nlps: 27, switchFlag: 0, },
+  { qe: 0x0AC1, nmps: 31, nlps: 28, switchFlag: 0, },
+  { qe: 0x09C1, nmps: 32, nlps: 29, switchFlag: 0, },
+  { qe: 0x08A1, nmps: 33, nlps: 30, switchFlag: 0, },
+  { qe: 0x0521, nmps: 34, nlps: 31, switchFlag: 0, },
+  { qe: 0x0441, nmps: 35, nlps: 32, switchFlag: 0, },
+  { qe: 0x02A1, nmps: 36, nlps: 33, switchFlag: 0, },
+  { qe: 0x0221, nmps: 37, nlps: 34, switchFlag: 0, },
+  { qe: 0x0141, nmps: 38, nlps: 35, switchFlag: 0, },
+  { qe: 0x0111, nmps: 39, nlps: 36, switchFlag: 0, },
+  { qe: 0x0085, nmps: 40, nlps: 37, switchFlag: 0, },
+  { qe: 0x0049, nmps: 41, nlps: 38, switchFlag: 0, },
+  { qe: 0x0025, nmps: 42, nlps: 39, switchFlag: 0, },
+  { qe: 0x0015, nmps: 43, nlps: 40, switchFlag: 0, },
+  { qe: 0x0009, nmps: 44, nlps: 41, switchFlag: 0, },
+  { qe: 0x0005, nmps: 45, nlps: 42, switchFlag: 0, },
+  { qe: 0x0001, nmps: 45, nlps: 43, switchFlag: 0, },
+  { qe: 0x5601, nmps: 46, nlps: 46, switchFlag: 0, },
+];
+
+/**
+ * This class implements the QM Coder decoding as defined in
  *   JPEG 2000 Part I Final Committee Draft Version 1.0
  *   Annex C.3 Arithmetic decoding procedure
  * available at http://www.jpeg.org/public/fcd15444-1.pdf
@@ -21,60 +74,9 @@
  * The arithmetic decoder is used in conjunction with context models to decode
  * JPEG2000 and JBIG2 streams.
  */
-var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
-  // Table C-2
-  var QeTable = [
-    { qe: 0x5601, nmps: 1, nlps: 1, switchFlag: 1, },
-    { qe: 0x3401, nmps: 2, nlps: 6, switchFlag: 0, },
-    { qe: 0x1801, nmps: 3, nlps: 9, switchFlag: 0, },
-    { qe: 0x0AC1, nmps: 4, nlps: 12, switchFlag: 0, },
-    { qe: 0x0521, nmps: 5, nlps: 29, switchFlag: 0, },
-    { qe: 0x0221, nmps: 38, nlps: 33, switchFlag: 0, },
-    { qe: 0x5601, nmps: 7, nlps: 6, switchFlag: 1, },
-    { qe: 0x5401, nmps: 8, nlps: 14, switchFlag: 0, },
-    { qe: 0x4801, nmps: 9, nlps: 14, switchFlag: 0, },
-    { qe: 0x3801, nmps: 10, nlps: 14, switchFlag: 0, },
-    { qe: 0x3001, nmps: 11, nlps: 17, switchFlag: 0, },
-    { qe: 0x2401, nmps: 12, nlps: 18, switchFlag: 0, },
-    { qe: 0x1C01, nmps: 13, nlps: 20, switchFlag: 0, },
-    { qe: 0x1601, nmps: 29, nlps: 21, switchFlag: 0, },
-    { qe: 0x5601, nmps: 15, nlps: 14, switchFlag: 1, },
-    { qe: 0x5401, nmps: 16, nlps: 14, switchFlag: 0, },
-    { qe: 0x5101, nmps: 17, nlps: 15, switchFlag: 0, },
-    { qe: 0x4801, nmps: 18, nlps: 16, switchFlag: 0, },
-    { qe: 0x3801, nmps: 19, nlps: 17, switchFlag: 0, },
-    { qe: 0x3401, nmps: 20, nlps: 18, switchFlag: 0, },
-    { qe: 0x3001, nmps: 21, nlps: 19, switchFlag: 0, },
-    { qe: 0x2801, nmps: 22, nlps: 19, switchFlag: 0, },
-    { qe: 0x2401, nmps: 23, nlps: 20, switchFlag: 0, },
-    { qe: 0x2201, nmps: 24, nlps: 21, switchFlag: 0, },
-    { qe: 0x1C01, nmps: 25, nlps: 22, switchFlag: 0, },
-    { qe: 0x1801, nmps: 26, nlps: 23, switchFlag: 0, },
-    { qe: 0x1601, nmps: 27, nlps: 24, switchFlag: 0, },
-    { qe: 0x1401, nmps: 28, nlps: 25, switchFlag: 0, },
-    { qe: 0x1201, nmps: 29, nlps: 26, switchFlag: 0, },
-    { qe: 0x1101, nmps: 30, nlps: 27, switchFlag: 0, },
-    { qe: 0x0AC1, nmps: 31, nlps: 28, switchFlag: 0, },
-    { qe: 0x09C1, nmps: 32, nlps: 29, switchFlag: 0, },
-    { qe: 0x08A1, nmps: 33, nlps: 30, switchFlag: 0, },
-    { qe: 0x0521, nmps: 34, nlps: 31, switchFlag: 0, },
-    { qe: 0x0441, nmps: 35, nlps: 32, switchFlag: 0, },
-    { qe: 0x02A1, nmps: 36, nlps: 33, switchFlag: 0, },
-    { qe: 0x0221, nmps: 37, nlps: 34, switchFlag: 0, },
-    { qe: 0x0141, nmps: 38, nlps: 35, switchFlag: 0, },
-    { qe: 0x0111, nmps: 39, nlps: 36, switchFlag: 0, },
-    { qe: 0x0085, nmps: 40, nlps: 37, switchFlag: 0, },
-    { qe: 0x0049, nmps: 41, nlps: 38, switchFlag: 0, },
-    { qe: 0x0025, nmps: 42, nlps: 39, switchFlag: 0, },
-    { qe: 0x0015, nmps: 43, nlps: 40, switchFlag: 0, },
-    { qe: 0x0009, nmps: 44, nlps: 41, switchFlag: 0, },
-    { qe: 0x0005, nmps: 45, nlps: 42, switchFlag: 0, },
-    { qe: 0x0001, nmps: 45, nlps: 43, switchFlag: 0, },
-    { qe: 0x5601, nmps: 46, nlps: 46, switchFlag: 0, }
-  ];
-
+class ArithmeticDecoder {
   // C.3.5 Initialisation of the decoder (INITDEC)
-  function ArithmeticDecoder(data, start, end) {
+  constructor(data, start, end) {
     this.data = data;
     this.bp = start;
     this.dataEnd = end;
@@ -90,95 +92,92 @@ var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
     this.a = 0x8000;
   }
 
-  ArithmeticDecoder.prototype = {
-    // C.3.4 Compressed data input (BYTEIN)
-    byteIn: function ArithmeticDecoder_byteIn() {
-      var data = this.data;
-      var bp = this.bp;
-      if (data[bp] === 0xFF) {
-        var b1 = data[bp + 1];
-        if (b1 > 0x8F) {
-          this.clow += 0xFF00;
-          this.ct = 8;
-        } else {
-          bp++;
-          this.clow += (data[bp] << 9);
-          this.ct = 7;
-          this.bp = bp;
-        }
+  // C.3.4 Compressed data input (BYTEIN)
+  byteIn() {
+    const data = this.data;
+    let bp = this.bp;
+
+    if (data[bp] === 0xFF) {
+      if (data[bp + 1] > 0x8F) {
+        this.clow += 0xFF00;
+        this.ct = 8;
       } else {
         bp++;
-        this.clow += bp < this.dataEnd ? (data[bp] << 8) : 0xFF00;
-        this.ct = 8;
+        this.clow += (data[bp] << 9);
+        this.ct = 7;
         this.bp = bp;
       }
-      if (this.clow > 0xFFFF) {
-        this.chigh += (this.clow >> 16);
-        this.clow &= 0xFFFF;
-      }
-    },
-    // C.3.2 Decoding a decision (DECODE)
-    readBit: function ArithmeticDecoder_readBit(contexts, pos) {
-      // contexts are packed into 1 byte:
-      // highest 7 bits carry cx.index, lowest bit carries cx.mps
-      var cx_index = contexts[pos] >> 1, cx_mps = contexts[pos] & 1;
-      var qeTableIcx = QeTable[cx_index];
-      var qeIcx = qeTableIcx.qe;
-      var d;
-      var a = this.a - qeIcx;
+    } else {
+      bp++;
+      this.clow += bp < this.dataEnd ? (data[bp] << 8) : 0xFF00;
+      this.ct = 8;
+      this.bp = bp;
+    }
+    if (this.clow > 0xFFFF) {
+      this.chigh += (this.clow >> 16);
+      this.clow &= 0xFFFF;
+    }
+  }
 
-      if (this.chigh < qeIcx) {
-        // exchangeLps
-        if (a < qeIcx) {
-          a = qeIcx;
-          d = cx_mps;
-          cx_index = qeTableIcx.nmps;
-        } else {
-          a = qeIcx;
-          d = 1 ^ cx_mps;
-          if (qeTableIcx.switchFlag === 1) {
-            cx_mps = d;
-          }
-          cx_index = qeTableIcx.nlps;
-        }
+  // C.3.2 Decoding a decision (DECODE)
+  readBit(contexts, pos) {
+    // Contexts are packed into 1 byte:
+    // highest 7 bits carry cx.index, lowest bit carries cx.mps
+    let cx_index = contexts[pos] >> 1, cx_mps = contexts[pos] & 1;
+    const qeTableIcx = QeTable[cx_index];
+    const qeIcx = qeTableIcx.qe;
+    let d;
+    let a = this.a - qeIcx;
+
+    if (this.chigh < qeIcx) {
+      // exchangeLps
+      if (a < qeIcx) {
+        a = qeIcx;
+        d = cx_mps;
+        cx_index = qeTableIcx.nmps;
       } else {
-        this.chigh -= qeIcx;
-        if ((a & 0x8000) !== 0) {
-          this.a = a;
-          return cx_mps;
-        }
-        // exchangeMps
-        if (a < qeIcx) {
-          d = 1 ^ cx_mps;
-          if (qeTableIcx.switchFlag === 1) {
-            cx_mps = d;
-          }
-          cx_index = qeTableIcx.nlps;
-        } else {
-          d = cx_mps;
-          cx_index = qeTableIcx.nmps;
+        a = qeIcx;
+        d = 1 ^ cx_mps;
+        if (qeTableIcx.switchFlag === 1) {
+          cx_mps = d;
         }
+        cx_index = qeTableIcx.nlps;
       }
-      // C.3.3 renormD;
-      do {
-        if (this.ct === 0) {
-          this.byteIn();
+    } else {
+      this.chigh -= qeIcx;
+      if ((a & 0x8000) !== 0) {
+        this.a = a;
+        return cx_mps;
+      }
+      // exchangeMps
+      if (a < qeIcx) {
+        d = 1 ^ cx_mps;
+        if (qeTableIcx.switchFlag === 1) {
+          cx_mps = d;
         }
+        cx_index = qeTableIcx.nlps;
+      } else {
+        d = cx_mps;
+        cx_index = qeTableIcx.nmps;
+      }
+    }
+    // C.3.3 renormD;
+    do {
+      if (this.ct === 0) {
+        this.byteIn();
+      }
 
-        a <<= 1;
-        this.chigh = ((this.chigh << 1) & 0xFFFF) | ((this.clow >> 15) & 1);
-        this.clow = (this.clow << 1) & 0xFFFF;
-        this.ct--;
-      } while ((a & 0x8000) === 0);
-      this.a = a;
+      a <<= 1;
+      this.chigh = ((this.chigh << 1) & 0xFFFF) | ((this.clow >> 15) & 1);
+      this.clow = (this.clow << 1) & 0xFFFF;
+      this.ct--;
+    } while ((a & 0x8000) === 0);
+    this.a = a;
 
-      contexts[pos] = cx_index << 1 | cx_mps;
-      return d;
-    },
-  };
-
-  return ArithmeticDecoder;
-})();
+    contexts[pos] = cx_index << 1 | cx_mps;
+    return d;
+  }
+}
 
 export {
   ArithmeticDecoder,