diff --git a/.eslintignore b/.eslintignore
index cc303851bff2..7fcd8b617e12 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -130,8 +130,6 @@ dom/workers/test/importScripts_worker_imported3.js
 dom/workers/test/invalid.js
 dom/workers/test/threadErrors_worker1.js
 
-# intl/ exclusions
-intl/uconv/
 # Bug 1527075: This directory is linted in github repository
 intl/l10n/
 
diff --git a/intl/uconv/tests/test_long_doc.html b/intl/uconv/tests/test_long_doc.html
index 88c8d697d809..cf07e7832fd2 100644
--- a/intl/uconv/tests/test_long_doc.html
+++ b/intl/uconv/tests/test_long_doc.html
@@ -64,14 +64,13 @@ var decoders = [
     "UTF-8"
 ];
 
-var decoder;
 for (var i = 0; i < decoders.length; i++) {
     var decoder = decoders[i];
     var data = encodeURI(testContent);
     var dataURI = "data:text/html;charset=" + decoder + "," + data;
-   
+
     var testFrame = document.createElement("iframe");
-    frameID = decoder;
+    let frameID = decoder;
     testFrame.setAttribute("id", frameID);
     var testFrameObj = document.body.appendChild(testFrame);
     if (i < decoders.length)
diff --git a/intl/uconv/tests/test_unicode_noncharacterescapes.html b/intl/uconv/tests/test_unicode_noncharacterescapes.html
index d531b082bb0b..e44f8d782b7a 100644
--- a/intl/uconv/tests/test_unicode_noncharacterescapes.html
+++ b/intl/uconv/tests/test_unicode_noncharacterescapes.html
@@ -13,6 +13,8 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=445886
 <pre id="test">
 <script class="testbody" type="text/javascript">
 
+/* eslint-disable no-eval */
+
 /** Test that unicode non-characters are not discarded **/
 function test()
 {
@@ -20,6 +22,7 @@ function test()
     SimpleTest.finish();
 }
 
+// eslint-disable-next-line complexity
 function Inject()
 {
     // script fragments containing Unicode non-characters
diff --git a/intl/uconv/tests/test_unicode_noncharacters_gb18030.html b/intl/uconv/tests/test_unicode_noncharacters_gb18030.html
index d293f591814d..0c9156d9e304 100644
--- a/intl/uconv/tests/test_unicode_noncharacters_gb18030.html
+++ b/intl/uconv/tests/test_unicode_noncharacters_gb18030.html
@@ -13,6 +13,8 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=445886
 <body onload="Inject()">
 <pre id="test"><script class="testbody" type="text/javascript">
 
+/* eslint-disable no-eval */
+
 /** Test that unicode non-characters are not discarded **/
 function test()
 {
@@ -20,272 +22,273 @@ function test()
     SimpleTest.finish();
 }
 
+// eslint-disable-next-line complexity
 function Inject()
 {
     // script fragments containing Unicode non-characters
     try {
         // U+FDD0
-        eval("$(\"display\").inner„0ú2HTML += \" U+FDD0 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½2HTML += \" U+FDD0 is evil \"");
     } catch(e) {}
     try {
         // U+FDD1
-        eval("$(\"display\").inner„0ú3HTML += \" U+FDD1 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½3HTML += \" U+FDD1 is evil \"");
     } catch(e) {}
     try {
         // U+FDD2
-        eval("$(\"display\").inner„0ú4HTML += \" U+FDD2 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½4HTML += \" U+FDD2 is evil \"");
     } catch(e) {}
     try {
         // U+FDD3
-        eval("$(\"display\").inner„0ú5HTML += \" U+FDD3 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½5HTML += \" U+FDD3 is evil \"");
     } catch(e) {}
     try {
         // U+FDD4
-        eval("$(\"display\").inner„0ú6HTML += \" U+FDD4 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½6HTML += \" U+FDD4 is evil \"");
     } catch(e) {}
     try {
         // U+FDD5
-        eval("$(\"display\").inner„0ú7HTML += \" U+FDD5 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½7HTML += \" U+FDD5 is evil \"");
     } catch(e) {}
     try {
         // U+FDD6
-        eval("$(\"display\").inner„0ú8HTML += \" U+FDD6 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½8HTML += \" U+FDD6 is evil \"");
     } catch(e) {}
     try {
         // U+FDD7
-        eval("$(\"display\").inner„0ú9HTML += \" U+FDD7 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½9HTML += \" U+FDD7 is evil \"");
     } catch(e) {}
     try {
         // U+FDD8
-        eval("$(\"display\").inner„0û0HTML += \" U+FDD8 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½0HTML += \" U+FDD8 is evil \"");
     } catch(e) {}
     try {
         // U+FDD9
-        eval("$(\"display\").inner„0û1HTML += \" U+FDD9 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½1HTML += \" U+FDD9 is evil \"");
     } catch(e) {}
     try {
         // U+FDDA
-        eval("$(\"display\").inner„0û2HTML += \" U+FDDA is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½2HTML += \" U+FDDA is evil \"");
     } catch(e) {}
     try {
         // U+FDDB
-        eval("$(\"display\").inner„0û3HTML += \" U+FDDB is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½3HTML += \" U+FDDB is evil \"");
     } catch(e) {}
     try {
         // U+FDDC
-        eval("$(\"display\").inner„0û4HTML += \" U+FDDC is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½4HTML += \" U+FDDC is evil \"");
     } catch(e) {}
     try {
         // U+FDDD
-        eval("$(\"display\").inner„0û5HTML += \" U+FDDD is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½5HTML += \" U+FDDD is evil \"");
     } catch(e) {}
     try {
         // U+FDDE
-        eval("$(\"display\").inner„0û6HTML += \" U+FDDE is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½6HTML += \" U+FDDE is evil \"");
     } catch(e) {}
     try {
         // U+FDDF
-        eval("$(\"display\").inner„0û7HTML += \" U+FDDF is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½7HTML += \" U+FDDF is evil \"");
     } catch(e) {}
     try {
         // U+FDE0
-        eval("$(\"display\").inner„0û8HTML += \" U+FDE0 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½8HTML += \" U+FDE0 is evil \"");
     } catch(e) {}
     try {
         // U+FDE1
-        eval("$(\"display\").inner„0û9HTML += \" U+FDE1 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½9HTML += \" U+FDE1 is evil \"");
     } catch(e) {}
     try {
         // U+FDE2
-        eval("$(\"display\").inner„0ü0HTML += \" U+FDE2 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½0HTML += \" U+FDE2 is evil \"");
     } catch(e) {}
     try {
         // U+FDE3
-        eval("$(\"display\").inner„0ü1HTML += \" U+FDE3 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½1HTML += \" U+FDE3 is evil \"");
     } catch(e) {}
     try {
         // U+FDE4
-        eval("$(\"display\").inner„0ü2HTML += \" U+FDE4 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½2HTML += \" U+FDE4 is evil \"");
     } catch(e) {}
     try {
         // U+FDE5
-        eval("$(\"display\").inner„0ü3HTML += \" U+FDE5 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½3HTML += \" U+FDE5 is evil \"");
     } catch(e) {}
     try {
         // U+FDE6
-        eval("$(\"display\").inner„0ü4HTML += \" U+FDE6 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½4HTML += \" U+FDE6 is evil \"");
     } catch(e) {}
     try {
         // U+FDE7
-        eval("$(\"display\").inner„0ü5HTML += \" U+FDE7 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½5HTML += \" U+FDE7 is evil \"");
     } catch(e) {}
     try {
         // U+FDE8
-        eval("$(\"display\").inner„0ü6HTML += \" U+FDE8 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½6HTML += \" U+FDE8 is evil \"");
     } catch(e) {}
     try {
         // U+FDE9
-        eval("$(\"display\").inner„0ü7HTML += \" U+FDE9 is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½7HTML += \" U+FDE9 is evil \"");
     } catch(e) {}
     try {
         // U+FDEA
-        eval("$(\"display\").inner„0ü8HTML += \" U+FDEA is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½8HTML += \" U+FDEA is evil \"");
     } catch(e) {}
     try {
         // U+FDEB
-        eval("$(\"display\").inner„0ü9HTML += \" U+FDEB is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½9HTML += \" U+FDEB is evil \"");
     } catch(e) {}
     try {
         // U+FDEC
-        eval("$(\"display\").inner„0ý0HTML += \" U+FDEC is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½0HTML += \" U+FDEC is evil \"");
     } catch(e) {}
     try {
         // U+FDED
-        eval("$(\"display\").inner„0ý1HTML += \" U+FDED is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½1HTML += \" U+FDED is evil \"");
     } catch(e) {}
     try {
         // U+FDEE
-        eval("$(\"display\").inner„0ý2HTML += \" U+FDEE is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½2HTML += \" U+FDEE is evil \"");
     } catch(e) {}
     try {
         // U+FDEF
-        eval("$(\"display\").inner„0ý3HTML += \" U+FDEF is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½3HTML += \" U+FDEF is evil \"");
     } catch(e) {}
     try {
         // U+FFFE
-        eval("$(\"display\").inner„1¤8HTML += \" U+FFFE is evil \"");
+        eval("$(\"display\").innerï¿½1ï¿½8HTML += \" U+FFFE is evil \"");
     } catch(e) {}
     try {
         // U+FFFF
-        eval("$(\"display\").inner„1¤9HTML += \" U+FFFF is evil \"");
+        eval("$(\"display\").innerï¿½1ï¿½9HTML += \" U+FFFF is evil \"");
     } catch(e) {}
     try {
         // U+1FFFE
-        eval("$(\"display\").inner•2‚4HTML += \" U+1FFFE is evil \"");
+        eval("$(\"display\").innerï¿½2ï¿½4HTML += \" U+1FFFE is evil \"");
     } catch(e) {}
     try {
         // U+1FFFF
-        eval("$(\"display\").inner•2‚5HTML += \" U+1FFFF is evil \"");
+        eval("$(\"display\").innerï¿½2ï¿½5HTML += \" U+1FFFF is evil \"");
     } catch(e) {}
     try {
         // U+2FFFE
-        eval("$(\"display\").innerš4„0HTML += \" U+2FFFE is evil \"");
+        eval("$(\"display\").innerï¿½4ï¿½0HTML += \" U+2FFFE is evil \"");
     } catch(e) {}
     try {
         // U+2FFFF
-        eval("$(\"display\").innerš4„1HTML += \" U+2FFFF is evil \"");
+        eval("$(\"display\").innerï¿½4ï¿½1HTML += \" U+2FFFF is evil \"");
     } catch(e) {}
     try {
         // U+3FFFE
-        eval("$(\"display\").innerŸ6…6HTML += \" U+3FFFE is evil \"");
+        eval("$(\"display\").innerï¿½6ï¿½6HTML += \" U+3FFFE is evil \"");
     } catch(e) {}
     try {
         // U+3FFFF
-        eval("$(\"display\").innerŸ6…7HTML += \" U+3FFFF is evil \"");
+        eval("$(\"display\").innerï¿½6ï¿½7HTML += \" U+3FFFF is evil \"");
     } catch(e) {}
     try {
         // U+4FFFE
-        eval("$(\"display\").inner¤8‡2HTML += \" U+4FFFE is evil \"");
+        eval("$(\"display\").innerï¿½8ï¿½2HTML += \" U+4FFFE is evil \"");
     } catch(e) {}
     try {
         // U+4FFFF
-        eval("$(\"display\").inner¤8‡3HTML += \" U+4FFFF is evil \"");
+        eval("$(\"display\").innerï¿½8ï¿½3HTML += \" U+4FFFF is evil \"");
     } catch(e) {}
     try {
         // U+5FFFE
-        eval("$(\"display\").innerª0ˆ8HTML += \" U+5FFFE is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½8HTML += \" U+5FFFE is evil \"");
     } catch(e) {}
     try {
         // U+5FFFF
-        eval("$(\"display\").innerª0ˆ9HTML += \" U+5FFFF is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½9HTML += \" U+5FFFF is evil \"");
     } catch(e) {}
     try {
         // U+6FFFE
-        eval("$(\"display\").inner¯2Š4HTML += \" U+6FFFE is evil \"");
+        eval("$(\"display\").innerï¿½2ï¿½4HTML += \" U+6FFFE is evil \"");
     } catch(e) {}
     try {
         // U+6FFFF
-        eval("$(\"display\").inner¯2Š5HTML += \" U+6FFFF is evil \"");
+        eval("$(\"display\").innerï¿½2ï¿½5HTML += \" U+6FFFF is evil \"");
     } catch(e) {}
     try {
         // U+7FFFE
-        eval("$(\"display\").inner´4Œ0HTML += \" U+7FFFE is evil \"");
+        eval("$(\"display\").innerï¿½4ï¿½0HTML += \" U+7FFFE is evil \"");
     } catch(e) {}
     try {
         // U+7FFFF
-        eval("$(\"display\").inner´4Œ1HTML += \" U+7FFFF is evil \"");
+        eval("$(\"display\").innerï¿½4ï¿½1HTML += \" U+7FFFF is evil \"");
     } catch(e) {}
     try {
         // U+8FFFE
-        eval("$(\"display\").inner¹66HTML += \" U+8FFFE is evil \"");
+        eval("$(\"display\").innerï¿½6ï¿½6HTML += \" U+8FFFE is evil \"");
     } catch(e) {}
     try {
         // U+8FFFF
-        eval("$(\"display\").inner¹67HTML += \" U+8FFFF is evil \"");
+        eval("$(\"display\").innerï¿½6ï¿½7HTML += \" U+8FFFF is evil \"");
     } catch(e) {}
     try {
         // U+9FFFE
-        eval("$(\"display\").inner¾82HTML += \" U+9FFFE is evil \"");
+        eval("$(\"display\").innerï¿½8ï¿½2HTML += \" U+9FFFE is evil \"");
     } catch(e) {}
     try {
         // U+9FFFF
-        eval("$(\"display\").inner¾83HTML += \" U+9FFFF is evil \"");
+        eval("$(\"display\").innerï¿½8ï¿½3HTML += \" U+9FFFF is evil \"");
     } catch(e) {}
     try {
         // U+AFFFE
-        eval("$(\"display\").innerÄ08HTML += \" U+AFFFE is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½8HTML += \" U+AFFFE is evil \"");
     } catch(e) {}
     try {
         // U+AFFFF
-        eval("$(\"display\").innerÄ09HTML += \" U+AFFFF is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½9HTML += \" U+AFFFF is evil \"");
     } catch(e) {}
     try {
         // U+BFFFE
-        eval("$(\"display\").innerÉ2’4HTML += \" U+BFFFE is evil \"");
+        eval("$(\"display\").innerï¿½2ï¿½4HTML += \" U+BFFFE is evil \"");
     } catch(e) {}
     try {
         // U+BFFFF
-        eval("$(\"display\").innerÉ2’5HTML += \" U+BFFFF is evil \"");
+        eval("$(\"display\").innerï¿½2ï¿½5HTML += \" U+BFFFF is evil \"");
     } catch(e) {}
     try {
         // U+CFFFE
-        eval("$(\"display\").innerÎ4”0HTML += \" U+CFFFE is evil \"");
+        eval("$(\"display\").innerï¿½4ï¿½0HTML += \" U+CFFFE is evil \"");
     } catch(e) {}
     try {
         // U+CFFFF
-        eval("$(\"display\").innerÎ4”1HTML += \" U+CFFFF is evil \"");
+        eval("$(\"display\").innerï¿½4ï¿½1HTML += \" U+CFFFF is evil \"");
     } catch(e) {}
     try {
         // U+DFFFE
-        eval("$(\"display\").innerÓ6•6HTML += \" U+DFFFE is evil \"");
+        eval("$(\"display\").innerï¿½6ï¿½6HTML += \" U+DFFFE is evil \"");
     } catch(e) {}
     try {
         // U+DFFFF
-        eval("$(\"display\").innerÓ6•7HTML += \" U+DFFFF is evil \"");
+        eval("$(\"display\").innerï¿½6ï¿½7HTML += \" U+DFFFF is evil \"");
     } catch(e) {}
     try {
         // U+EFFFE
-        eval("$(\"display\").innerØ8—2HTML += \" U+EFFFE is evil \"");
+        eval("$(\"display\").innerï¿½8ï¿½2HTML += \" U+EFFFE is evil \"");
     } catch(e) {}
     try {
         // U+EFFFF
-        eval("$(\"display\").innerØ8—3HTML += \" U+EFFFF is evil \"");
+        eval("$(\"display\").innerï¿½8ï¿½3HTML += \" U+EFFFF is evil \"");
     } catch(e) {}
     try {
         // U+FFFFE
-        eval("$(\"display\").innerÞ0˜8HTML += \" U+FFFFE is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½8HTML += \" U+FFFFE is evil \"");
     } catch(e) {}
     try {
         // U+FFFFF
-        eval("$(\"display\").innerÞ0˜9HTML += \" U+FFFFF is evil \"");
+        eval("$(\"display\").innerï¿½0ï¿½9HTML += \" U+FFFFF is evil \"");
     } catch(e) {}
     try {
         // U+10FFFE
-        eval("$(\"display\").innerã2š4HTML += \" U+10FFFE is evil \"");
+        eval("$(\"display\").innerï¿½2ï¿½4HTML += \" U+10FFFE is evil \"");
     } catch(e) {}
     try {
         // U+10FFFF
-        eval("$(\"display\").innerã2š5HTML += \" U+10FFFF is evil \"");
+        eval("$(\"display\").innerï¿½2ï¿½5HTML += \" U+10FFFF is evil \"");
     } catch(e) {}
     test();
 }
diff --git a/intl/uconv/tests/test_unicode_noncharacters_utf8.html b/intl/uconv/tests/test_unicode_noncharacters_utf8.html
index 3e8b54fb0747..ecfdbeae09bf 100644
--- a/intl/uconv/tests/test_unicode_noncharacters_utf8.html
+++ b/intl/uconv/tests/test_unicode_noncharacters_utf8.html
@@ -13,6 +13,8 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=445886
 <pre id="test">
 <script class="testbody" type="text/javascript">
 
+/* eslint-disable no-eval */
+
 /** Test that unicode non-characters are not discarded **/
 function test()
 {
@@ -20,6 +22,7 @@ function test()
     SimpleTest.finish();
 }
 
+// eslint-disable-next-line complexity
 function Inject()
 {
     // script fragments containing Unicode non-characters
diff --git a/intl/uconv/tests/unit/head_charsetConversionTests.js b/intl/uconv/tests/unit/head_charsetConversionTests.js
index 4fbf6e9af725..1f983f917c84 100644
--- a/intl/uconv/tests/unit/head_charsetConversionTests.js
+++ b/intl/uconv/tests/unit/head_charsetConversionTests.js
@@ -1,3 +1,5 @@
+const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
+
 var CC = Components.Constructor;
 
 function CreateScriptableConverter() {
diff --git a/intl/uconv/tests/unit/test_bug317216.js b/intl/uconv/tests/unit/test_bug317216.js
index 3cf0b2f63da0..507e492bbe9b 100644
--- a/intl/uconv/tests/unit/test_bug317216.js
+++ b/intl/uconv/tests/unit/test_bug317216.js
@@ -112,7 +112,7 @@ function testCase(testText, expectedText, bufferLength, charset) {
   );
 
   if (!(testConverter instanceof Ci.nsIUnicharLineInputStream)) {
-    throw "not line input stream";
+    throw new Error("not line input stream");
   }
 
   var outStr = "";
diff --git a/intl/uconv/tests/unit/test_bug340714.js b/intl/uconv/tests/unit/test_bug340714.js
index d56bbaafe19c..feba35c37fe8 100644
--- a/intl/uconv/tests/unit/test_bug340714.js
+++ b/intl/uconv/tests/unit/test_bug340714.js
@@ -12,7 +12,6 @@
  */
 
 const { NetUtil } = ChromeUtils.import("resource://gre/modules/NetUtil.jsm");
-const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
 
 const beBOM = "%FE%FF";
 const leBOM = "%FF%FE";
@@ -29,6 +28,7 @@ registerCleanupFunction(() => {
 });
 
 function makeText(withBOM, charset) {
+  // eslint-disable-next-line no-eval
   var theText = eval("sample" + charset);
   if (withBOM) {
     if (charset == "UTF16BE") {
@@ -63,7 +63,7 @@ function testCase(withBOM, charset, charsetDec, decoder, bufferLength) {
   );
 
   if (!(testConverter instanceof Ci.nsIUnicharLineInputStream)) {
-    throw "not line input stream";
+    throw new Error("not line input stream");
   }
 
   var outStr = "";
@@ -90,7 +90,7 @@ function testCase(withBOM, charset, charsetDec, decoder, bufferLength) {
         "\n"
     );
     if (outStr.length == expected.length) {
-      for (i = 0; i < outStr.length; ++i) {
+      for (let i = 0; i < outStr.length; ++i) {
         if (outStr.charCodeAt(i) != expected.charCodeAt(i)) {
           dump(
             i +
diff --git a/intl/uconv/tests/unit/test_bug522931.js b/intl/uconv/tests/unit/test_bug522931.js
index b8be5178bc61..2dae8d72e9f7 100644
--- a/intl/uconv/tests/unit/test_bug522931.js
+++ b/intl/uconv/tests/unit/test_bug522931.js
@@ -1,7 +1,4 @@
 // crash test with invaild parameter (bug 522931)
 function run_test() {
-  var textToSubURI = Cc["@mozilla.org/intl/texttosuburi;1"].getService(
-    Ci.nsITextToSubURI
-  );
-  Assert.equal(textToSubURI.UnEscapeAndConvert("UTF-8", null), "");
+  Assert.equal(Services.textToSubURI.UnEscapeAndConvert("UTF-8", null), "");
 }
diff --git a/intl/uconv/tests/unit/test_bug563618.js b/intl/uconv/tests/unit/test_bug563618.js
index 46503fcbdf15..2fa077034495 100644
--- a/intl/uconv/tests/unit/test_bug563618.js
+++ b/intl/uconv/tests/unit/test_bug563618.js
@@ -54,7 +54,7 @@ function testCase(testText, expectedText, bufferLength, charset) {
   );
 
   if (!(testConverter instanceof Ci.nsIUnicharLineInputStream)) {
-    throw "not line input stream";
+    throw new Error("not line input stream");
   }
 
   var outStr = "";
@@ -69,7 +69,7 @@ function testCase(testText, expectedText, bufferLength, charset) {
   if (outStr != expectedText) {
     dump("Failed with bufferLength = " + bufferLength + "\n");
     if (outStr.length == expectedText.length) {
-      for (i = 0; i < outStr.length; ++i) {
+      for (let i = 0; i < outStr.length; ++i) {
         if (outStr.charCodeAt(i) != expectedText.charCodeAt(i)) {
           dump(
             i +
diff --git a/intl/uconv/tests/unit/test_bug715319.gb2312.js b/intl/uconv/tests/unit/test_bug715319.gb2312.js
index f23b89c51bb6..f780ab81d178 100644
--- a/intl/uconv/tests/unit/test_bug715319.gb2312.js
+++ b/intl/uconv/tests/unit/test_bug715319.gb2312.js
@@ -32,14 +32,14 @@ function test(inString) {
 
   var outLen = outString.length;
   for (var pos = 1; pos < 3; ++pos) {
-    outPos = outLen - (9 - pos);
+    let outPos = outLen - (9 - pos);
     if (outPos < 0) {
       outPos = 0;
     }
-    c0 = inString.charCodeAt(0);
-    c1 = inString.charCodeAt(1);
-    c2 = inString.charCodeAt(2);
-    c3 = inString.charCodeAt(3);
+    let c0 = inString.charCodeAt(0);
+    let c1 = inString.charCodeAt(1);
+    let c2 = inString.charCodeAt(2);
+    let c3 = inString.charCodeAt(3);
     if (
       IsASCII(inString.charCodeAt(pos)) &&
       !(
diff --git a/intl/uconv/tests/unit/test_charset_conversion.js b/intl/uconv/tests/unit/test_charset_conversion.js
index 00a1aefaa247..8f1793ca1858 100644
--- a/intl/uconv/tests/unit/test_charset_conversion.js
+++ b/intl/uconv/tests/unit/test_charset_conversion.js
@@ -129,7 +129,12 @@ function getUnicharInputStream(filename, encoding) {
   file.append(filename);
 
   const PR_RDONLY = 0x1;
-  var fis = new FIS(file, PR_RDONLY, 0644, Ci.nsIFileInputStream.CLOSE_ON_EOF);
+  var fis = new FIS(
+    file,
+    PR_RDONLY,
+    "0644",
+    Ci.nsIFileInputStream.CLOSE_ON_EOF
+  );
   return new CIS(fis, encoding, 8192, 0x0);
 }
 
@@ -138,13 +143,17 @@ function getBinaryInputStream(filename, encoding) {
   file.append(filename);
 
   const PR_RDONLY = 0x1;
-  var fis = new FIS(file, PR_RDONLY, 0644, Ci.nsIFileInputStream.CLOSE_ON_EOF);
+  var fis = new FIS(
+    file,
+    PR_RDONLY,
+    "0644",
+    Ci.nsIFileInputStream.CLOSE_ON_EOF
+  );
   return new BIS(fis);
 }
 
 function equalStreams(stream, codePoints) {
-  var sz,
-    currIndex = 0;
+  var currIndex = 0;
   while (true) {
     var unit = stream.readUnit();
     if (unit < 0) {
@@ -154,7 +163,7 @@ function equalStreams(stream, codePoints) {
       return false;
     }
   }
-
+  // eslint-disable-next-line no-unreachable
   do_throw("not reached");
   return false;
 }
@@ -179,6 +188,7 @@ function equalUnicharStreams(s1, s2) {
   }
 
   // not reached
+  // eslint-disable-next-line no-unreachable
   return false;
 }
 
diff --git a/intl/uconv/tests/unit/test_unEscapeNonAsciiURI.js b/intl/uconv/tests/unit/test_unEscapeNonAsciiURI.js
index 6ae3234773fe..f4479592444d 100644
--- a/intl/uconv/tests/unit/test_unEscapeNonAsciiURI.js
+++ b/intl/uconv/tests/unit/test_unEscapeNonAsciiURI.js
@@ -1,12 +1,11 @@
 // Tests for nsITextToSubURI.unEscapeNonAsciiURI
 function run_test() {
-  const textToSubURI = Cc["@mozilla.org/intl/texttosuburi;1"].getService(
-    Ci.nsITextToSubURI
-  );
-
   // Tests whether nsTextToSubURI does UTF-16 unescaping (it shouldn't)
   const testURI = "data:text/html,%FE%FF";
-  Assert.equal(textToSubURI.unEscapeNonAsciiURI("UTF-16", testURI), testURI);
+  Assert.equal(
+    Services.textToSubURI.unEscapeNonAsciiURI("UTF-16", testURI),
+    testURI
+  );
 
   // Tests whether incomplete multibyte sequences throw.
   const tests = [
@@ -44,14 +43,14 @@ function run_test() {
     if (t.throws !== undefined) {
       let thrown = undefined;
       try {
-        textToSubURI.unEscapeNonAsciiURI("UTF-8", t.input);
+        Services.textToSubURI.unEscapeNonAsciiURI("UTF-8", t.input);
       } catch (e) {
         thrown = e.result;
       }
       Assert.equal(thrown, t.throws);
     } else {
       Assert.equal(
-        textToSubURI.unEscapeNonAsciiURI("UTF-8", t.input),
+        Services.textToSubURI.unEscapeNonAsciiURI("UTF-8", t.input),
         t.expected
       );
     }
diff --git a/intl/uconv/tests/unit/test_utf8_illegals.js b/intl/uconv/tests/unit/test_utf8_illegals.js
index 6ccf9ca9e01f..8712b4c3e82c 100644
--- a/intl/uconv/tests/unit/test_utf8_illegals.js
+++ b/intl/uconv/tests/unit/test_utf8_illegals.js
@@ -136,7 +136,7 @@ function testCaseInputStream(inStr, expected) {
   );
 
   if (!(testConverter instanceof Ci.nsIUnicharLineInputStream)) {
-    throw "not line input stream";
+    throw new Error("not line input stream");
   }
 
   var outStr = "";
