diff --git a/src/core/ccitt_stream.js b/src/core/ccitt_stream.js
index 6eab57ae3..ced509334 100644
--- a/src/core/ccitt_stream.js
+++ b/src/core/ccitt_stream.js
@@ -12,13 +12,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-/* eslint-disable no-var */
 
 import { Dict, isDict } from "./primitives.js";
 import { CCITTFaxDecoder } from "./ccitt.js";
 import { DecodeStream } from "./stream.js";
 
-var CCITTFaxStream = (function CCITTFaxStreamClosure() {
+const CCITTFaxStream = (function CCITTFaxStreamClosure() {
   // eslint-disable-next-line no-shadow
   function CCITTFaxStream(str, maybeLength, params) {
     this.str = str;
diff --git a/src/core/glyphlist.js b/src/core/glyphlist.js
index 63785136f..c0878b080 100644
--- a/src/core/glyphlist.js
+++ b/src/core/glyphlist.js
@@ -13,11 +13,10 @@
  * limitations under the License.
  */
 /* no-babel-preset */
-/* eslint-disable no-var */
 
 import { getArrayLookupTableFactory } from "./core_utils.js";
 
-var getGlyphsUnicode = getArrayLookupTableFactory(function () {
+const getGlyphsUnicode = getArrayLookupTableFactory(function () {
   // prettier-ignore
   return [
     "A", 0x0041,
@@ -4347,7 +4346,7 @@ var getGlyphsUnicode = getArrayLookupTableFactory(function () {
   ];
 });
 
-var getDingbatsGlyphsUnicode = getArrayLookupTableFactory(function () {
+const getDingbatsGlyphsUnicode = getArrayLookupTableFactory(function () {
   // prettier-ignore
   return [
     "space", 0x0020,
diff --git a/src/core/metrics.js b/src/core/metrics.js
index e95d6316a..2d8650142 100644
--- a/src/core/metrics.js
+++ b/src/core/metrics.js
@@ -12,14 +12,13 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-/* eslint-disable no-var */
 
 import { getLookupTableFactory } from "./core_utils.js";
 
 // The Metrics object contains glyph widths (in glyph space units).
 // As per PDF spec, for most fonts (Type 3 being an exception) a glyph
 // space unit corresponds to 1/1000th of text space unit.
-var getMetrics = getLookupTableFactory(function (t) {
+const getMetrics = getLookupTableFactory(function (t) {
   t.Courier = 600;
   t["Courier-Bold"] = 600;
   t["Courier-BoldOblique"] = 600;
diff --git a/src/core/primitives.js b/src/core/primitives.js
index fece2d707..7e0d36ea2 100644
--- a/src/core/primitives.js
+++ b/src/core/primitives.js
@@ -12,13 +12,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-/* eslint-disable no-var */
 
 import { assert, unreachable } from "../shared/util.js";
 
-var EOF = {};
+const EOF = {};
 
-var Name = (function NameClosure() {
+const Name = (function NameClosure() {
   let nameCache = Object.create(null);
 
   // eslint-disable-next-line no-shadow
@@ -29,7 +28,7 @@ var Name = (function NameClosure() {
   Name.prototype = {};
 
   Name.get = function Name_get(name) {
-    var nameValue = nameCache[name];
+    const nameValue = nameCache[name];
     // eslint-disable-next-line no-restricted-syntax
     return nameValue ? nameValue : (nameCache[name] = new Name(name));
   };
@@ -41,7 +40,7 @@ var Name = (function NameClosure() {
   return Name;
 })();
 
-var Cmd = (function CmdClosure() {
+const Cmd = (function CmdClosure() {
   let cmdCache = Object.create(null);
 
   // eslint-disable-next-line no-shadow
@@ -52,7 +51,7 @@ var Cmd = (function CmdClosure() {
   Cmd.prototype = {};
 
   Cmd.get = function Cmd_get(cmd) {
-    var cmdValue = cmdCache[cmd];
+    const cmdValue = cmdCache[cmd];
     // eslint-disable-next-line no-restricted-syntax
     return cmdValue ? cmdValue : (cmdCache[cmd] = new Cmd(cmd));
   };
@@ -64,8 +63,8 @@ var Cmd = (function CmdClosure() {
   return Cmd;
 })();
 
-var Dict = (function DictClosure() {
-  var nonSerializable = function nonSerializableClosure() {
+const Dict = (function DictClosure() {
+  const nonSerializable = function nonSerializableClosure() {
     return nonSerializable; // creating closure on some variable
   };
 
@@ -165,7 +164,7 @@ var Dict = (function DictClosure() {
     },
 
     forEach: function Dict_forEach(callback) {
-      for (var key in this._map) {
+      for (const key in this._map) {
         callback(key, this.get(key));
       }
     },
@@ -240,7 +239,7 @@ var Dict = (function DictClosure() {
   return Dict;
 })();
 
-var Ref = (function RefClosure() {
+const Ref = (function RefClosure() {
   let refCache = Object.create(null);
 
   // eslint-disable-next-line no-shadow
diff --git a/src/core/unicode.js b/src/core/unicode.js
index 0e9aa8099..b9623308c 100644
--- a/src/core/unicode.js
+++ b/src/core/unicode.js
@@ -13,7 +13,6 @@
  * limitations under the License.
  */
 /* no-babel-preset */
-/* eslint-disable no-var */
 
 import {
   getArrayLookupTableFactory,
@@ -23,7 +22,7 @@ import {
 // Some characters, e.g. copyrightserif, are mapped to the private use area
 // and might not be displayed using standard fonts. Mapping/hacking well-known
 // chars to the similar equivalents in the normal characters range.
-var getSpecialPUASymbols = getLookupTableFactory(function (t) {
+const getSpecialPUASymbols = getLookupTableFactory(function (t) {
   t[63721] = 0x00a9; // copyrightsans (0xF8E9) => copyright
   t[63193] = 0x00a9; // copyrightserif (0xF6D9) => copyright
   t[63720] = 0x00ae; // registersans (0xF8E8) => registered
@@ -63,7 +62,7 @@ function mapSpecialUnicodeValues(code) {
 }
 
 function getUnicodeForGlyph(name, glyphsUnicodeMap) {
-  var unicode = glyphsUnicodeMap[name];
+  let unicode = glyphsUnicodeMap[name];
   if (unicode !== undefined) {
     return unicode;
   }
@@ -72,8 +71,8 @@ function getUnicodeForGlyph(name, glyphsUnicodeMap) {
   }
   // Try to recover valid Unicode values from 'uniXXXX'/'uXXXX{XX}' glyphs.
   if (name[0] === "u") {
-    var nameLen = name.length,
-      hexStr;
+    const nameLen = name.length;
+    let hexStr;
 
     if (nameLen === 7 && name[1] === "n" && name[2] === "i") {
       // 'uniXXXX'
@@ -95,7 +94,7 @@ function getUnicodeForGlyph(name, glyphsUnicodeMap) {
   return -1;
 }
 
-var UnicodeRanges = [
+const UnicodeRanges = [
   { begin: 0x0000, end: 0x007f }, // Basic Latin
   { begin: 0x0080, end: 0x00ff }, // Latin-1 Supplement
   { begin: 0x0100, end: 0x017f }, // Latin Extended-A
@@ -222,8 +221,8 @@ var UnicodeRanges = [
 ];
 
 function getUnicodeRangeFor(value) {
-  for (var i = 0, ii = UnicodeRanges.length; i < ii; i++) {
-    var range = UnicodeRanges[i];
+  for (let i = 0, ii = UnicodeRanges.length; i < ii; i++) {
+    const range = UnicodeRanges[i];
     if (value >= range.begin && value < range.end) {
       return i;
     }
@@ -232,7 +231,7 @@ function getUnicodeRangeFor(value) {
 }
 
 function isRTLRangeFor(value) {
-  var range = UnicodeRanges[13];
+  let range = UnicodeRanges[13];
   if (value >= range.begin && value < range.end) {
     return true;
   }
@@ -245,7 +244,7 @@ function isRTLRangeFor(value) {
 
 // The normalization table is obtained by filtering the Unicode characters
 // database with <compat> entries.
-var getNormalizedUnicodes = getArrayLookupTableFactory(function () {
+const getNormalizedUnicodes = getArrayLookupTableFactory(function () {
   // prettier-ignore
   return [
     "\u00A8", "\u0020\u0308",
@@ -1629,16 +1628,16 @@ var getNormalizedUnicodes = getArrayLookupTableFactory(function () {
 });
 
 function reverseIfRtl(chars) {
-  var charsLength = chars.length;
+  const charsLength = chars.length;
   // Reverse an arabic ligature.
   if (charsLength <= 1 || !isRTLRangeFor(chars.charCodeAt(0))) {
     return chars;
   }
-  var s = "";
-  for (var ii = charsLength - 1; ii >= 0; ii--) {
-    s += chars[ii];
+  const buf = [];
+  for (let ii = charsLength - 1; ii >= 0; ii--) {
+    buf.push(chars[ii]);
   }
-  return s;
+  return buf.join("");
 }
 
 export {