--- a/browser/base/content/tabbrowser.xml
+++ b/browser/base/content/tabbrowser.xml
@@ -5622,17 +5622,17 @@
 
             let scrollButtonWidth = this.mTabstrip._scrollButtonDown.getBoundingClientRect().width;
             let paddingStart = this.mTabstrip.scrollboxPaddingStart;
             let width = 0;
 
             for (let i = numPinned - 1; i >= 0; i--) {
               let tab = this.childNodes[i];
               width += tab.getBoundingClientRect().width;
-              tab.style.marginInlineStart = - (width + scrollButtonWidth + paddingStart) + "px";
+              tab.style.marginInlineStart = -(width + scrollButtonWidth + paddingStart) + "px";
             }
 
             this.style.paddingInlineStart = width + paddingStart + "px";
 
           } else {
             this.removeAttribute("positionpinnedtabs");
 
             for (let i = 0; i < numPinned; i++) {

--- a/browser/base/content/test/general/browser_gestureSupport.js
+++ b/browser/base/content/test/general/browser_gestureSupport.js
@@ -307,18 +307,18 @@ function test_emitLatchedEvents(eventPre
       let delta = Math.random() * (isIncreasing ? 100 : -100);
     test_utils.sendSimpleGestureEvent(eventPrefix + "Update", 0, 0, 0, delta, 0);
     cumulativeDelta += delta;
     checkBoth(2, "Increasing command was triggered", "Decreasing command was triggered");
   }
 
   // Now go back in the opposite direction.
   test_utils.sendSimpleGestureEvent(eventPrefix + "Update", 0, 0, 0,
-				    - initialDelta, 0);
-  cumulativeDelta += - initialDelta;
+				    -initialDelta, 0);
+  cumulativeDelta += -initialDelta;
   if (isIncreasing) {
     expect.dec++;
     checkBoth(3, "Increasing command was triggered", "Decreasing command was not triggered");
   } else {
     expect.inc++;
     checkBoth(3, "Increasing command was not triggered", "Decreasing command was triggered");
   }
 

--- a/browser/components/places/content/bookmarkProperties.js
+++ b/browser/components/places/content/bookmarkProperties.js
@@ -364,17 +364,17 @@ var BookmarkPropertiesPanel = {
           // Check uri fields to enable accept button if input is valid
           document.documentElement
                   .getButton("accept").disabled = !this._inputIsValid();
         }
         break;
       case "resize":
         for (let [id, oldHeight] of elementsHeight) {
           let newHeight = document.getElementById(id).boxObject.height;
-          this._height += - oldHeight + newHeight;
+          this._height += -oldHeight + newHeight;
           elementsHeight.set(id, newHeight);
         }
         break;
     }
   },
 
 	// Hack for implementing batched-Undo around the editBookmarkOverlay
 	// instant-apply code. For all the details see the comment above beginBatch

--- a/browser/components/preferences/translation.js
+++ b/browser/components/preferences/translation.js
@@ -135,17 +135,17 @@ var gTranslationExceptions = {
   },
 
   observe: function(aSubject, aTopic, aData) {
     if (aTopic == "perm-changed") {
       if (aData == "cleared") {
         if (!this._sites.length)
           return;
         let removed = this._sites.splice(0, this._sites.length);
-        this._siteTree.boxObject.rowCountChanged(0, - removed.length);
+        this._siteTree.boxObject.rowCountChanged(0, -removed.length);
       }
       else {
         let perm = aSubject.QueryInterface(Ci.nsIPermission);
         if (perm.type != kPermissionType)
           return;
 
         if (aData == "added") {
           if (perm.capability != Services.perms.DENY_ACTION)

--- a/toolkit/.eslintrc.js
+++ b/toolkit/.eslintrc.js
@@ -176,17 +176,23 @@ module.exports = {
 
     // No space padding in parentheses
     // "space-in-parens": ["error", "never"],
 
     // Require spaces around operators
     "space-infix-ops": ["error", { "int32Hint": false }],
 
     // ++ and -- should not need spacing
-    // "space-unary-ops": ["error", { "words": true, "nonwords": false }],
+    "space-unary-ops": ["error", {
+      "words": true,
+      "nonwords": false,
+      "overrides": {
+        "typeof": false // We tend to use typeof as a function call
+      }
+    }],
 
     // Requires or disallows a whitespace (space or tab) beginning a comment
     "spaced-comment": "error",
 
     // No comparisons to NaN
     "use-isnan": "error",
 
     // Only check typeof against valid results

--- a/toolkit/components/aboutcheckerboard/content/aboutCheckerboard.js
+++ b/toolkit/components/aboutcheckerboard/content/aboutCheckerboard.js
@@ -91,17 +91,17 @@ function loadData() {
 
     var charPos = 0;
     var lastLineLength = 0;
     var lines = trace.value.split(/\r|\n/);
     for (var i = 0; i < lines.length; i++) {
         charPos += lastLineLength;
         lastLineLength = lines[i].length + 1;
         // skip lines without RENDERTRACE
-        if (! /RENDERTRACE/.test(lines[i])) {
+        if (!/RENDERTRACE/.test(lines[i])) {
             continue;
         }
 
         var tokens = lines[i].split(/\s+/);
         var j = 0;
         // skip tokens until RENDERTRACE
         while (j < tokens.length && tokens[j++] != "RENDERTRACE"); // empty loop body
         if (j >= tokens.length - 2) {
@@ -158,32 +158,32 @@ function loadData() {
                 break;
 
             default:
                 log("Error parsing line " + lines[i]);
                 break;
         }
     }
 
-    if (! renderFrame()) {
+    if (!renderFrame()) {
         alert("No data found; nothing to render!");
     }
 }
 
 // render the current frame (i.e. renderData[currentFrame])
 // returns false if currentFrame is out of bounds, true otherwise
 function renderFrame() {
     var frame = currentFrame;
     if (frame < 0 || frame >= renderData.length) {
         log("Invalid frame index");
         return false;
     }
 
     var canvas = document.getElementById('canvas');
-    if (! canvas.getContext) {
+    if (!canvas.getContext) {
         log("No canvas context");
     }
 
     var context = canvas.getContext('2d');
 
     // midpoint of the bounding box
     var midX = (minX + maxX) / 2.0;
     var midY = (minY + maxY) / 2.0;
@@ -237,33 +237,33 @@ function reset(beginning) {
     renderFrame();
 }
 
 function step(backwards) {
     if (playing) {
         togglePlay();
     }
     currentFrame += (backwards ? -1 : 1);
-    if (! renderFrame()) {
+    if (!renderFrame()) {
         currentFrame -= (backwards ? -1 : 1);
     }
 }
 
 function pause() {
     clearInterval(timerId);
     playing = false;
 }
 
 function togglePlay() {
     if (playing) {
         pause();
     } else {
         timerId = setInterval(function() {
             currentFrame++;
-            if (! renderFrame()) {
+            if (!renderFrame()) {
                 currentFrame--;
                 togglePlay();
             }
         }, FRAME_INTERVAL_MS);
         playing = true;
     }
 }
 

--- a/toolkit/components/passwordmgr/test/chrome/test_privbrowsing_perwindowpb.html
+++ b/toolkit/components/passwordmgr/test/chrome/test_privbrowsing_perwindowpb.html
@@ -41,17 +41,17 @@ var subtests = [
                    "subtst_privbrowsing_4.html", // 9
                    "subtst_privbrowsing_3.html" // 10
                ];
 var observer;
 
 var testNum = 0;
 function loadNextTest() {
   // run the initialization code for each test
-  switch (++ testNum) {
+  switch (++testNum) {
     case 1:
       popupNotifications = normalWindowPopupNotifications;
       iframe = normalWindowIframe;
       break;
 
     case 2:
       popupNotifications = privateWindowPopupNotifications;
       iframe = privateWindowIframe;

--- a/toolkit/components/places/tests/unit/test_454977.js
+++ b/toolkit/components/places/tests/unit/test_454977.js
@@ -32,17 +32,17 @@ function* task_add_visit(aURI, aVisitTyp
   let visitId = yield deferUpdatePlaces;
 
   // Increase visit_count if applicable
   if (aVisitType != 0 &&
       aVisitType != TRANSITION_EMBED &&
       aVisitType != TRANSITION_FRAMED_LINK &&
       aVisitType != TRANSITION_DOWNLOAD &&
       aVisitType != TRANSITION_RELOAD) {
-    visit_count ++;
+    visit_count++;
   }
 
   // Get the place id
   if (visitId > 0) {
     let sql = "SELECT place_id FROM moz_historyvisits WHERE id = ?1";
     let stmt = DBConn().createStatement(sql);
     stmt.bindByIndex(0, visitId);
     do_check_true(stmt.executeStep());

--- a/toolkit/components/telemetry/TelemetryUtils.jsm
+++ b/toolkit/components/telemetry/TelemetryUtils.jsm
@@ -131,17 +131,17 @@ this.TelemetryUtils = {
       while (number.length < places) {
         number = "0" + number;
       }
       return number;
     }
 
     let sign = (n) => n >= 0 ? "+" : "-";
     // getTimezoneOffset counter-intuitively returns -60 for UTC+1.
-    let tzOffset = - date.getTimezoneOffset();
+    let tzOffset = -date.getTimezoneOffset();
 
     // YYYY-MM-DDThh:mm:ss.sTZD (eg 1997-07-16T19:20:30.45+01:00)
     return    padNumber(date.getFullYear(), 4)
       + "-" + padNumber(date.getMonth() + 1, 2)
       + "-" + padNumber(date.getDate(), 2)
       + "T" + padNumber(date.getHours(), 2)
       + ":" + padNumber(date.getMinutes(), 2)
       + ":" + padNumber(date.getSeconds(), 2)

--- a/toolkit/components/telemetry/tests/unit/test_TelemetrySend.js
+++ b/toolkit/components/telemetry/tests/unit/test_TelemetrySend.js
@@ -41,17 +41,17 @@ function waitForTimer() {
 }
 
 // Allow easy faking of readable ping ids.
 // This helps with debugging issues with e.g. ordering in the send logic.
 function fakePingId(type, number) {
   const HEAD = "93bd0011-2c8f-4e1c-bee0-";
   const TAIL = "000000000000";
   const N = String(number);
-  const id = HEAD + type + TAIL.slice(type.length, - N.length) + N;
+  const id = HEAD + type + TAIL.slice(type.length, -N.length) + N;
   fakeGeneratePingId(() => id);
   return id;
 }
 
 var checkPingsSaved = Task.async(function* (pingIds) {
   let allFound = true;
   for (let id of pingIds) {
     const path = OS.Path.join(TelemetryStorage.pingDirectoryPath, id);

--- a/toolkit/content/widgets/datetimepicker.xml
+++ b/toolkit/content/widgets/datetimepicker.xml
@@ -179,17 +179,17 @@
             this._lastFocusedField = target;
         ]]>
       </handler>
 
       <handler event="keypress">
         <![CDATA[
           if (this._hasEntry && event.charCode &&
               this._currentField != this._fieldAMPM &&
-	      ! (event.altKey || event.ctrlKey || event.metaKey) &&
+	            !(event.altKey || event.ctrlKey || event.metaKey) &&
               (event.charCode < 48 || event.charCode > 57))
             event.preventDefault();
         ]]>
       </handler>
 
       <handler event="keypress" keycode="VK_UP">
         if (this._hasEntry)
           this._increaseOrDecrease(1);

--- a/toolkit/content/widgets/textbox.xml
+++ b/toolkit/content/widgets/textbox.xml
@@ -499,17 +499,17 @@
         </body>
       </method>
 
       <method name="_setMenuItemVisibility">
         <parameter name="anonid"/>
         <parameter name="visible"/>
         <body><![CDATA[
           document.getAnonymousElementByAttribute(this, "anonid", anonid).
-            hidden = ! visible;
+            hidden = !visible;
         ]]></body>
       </method>
 
       <method name="doCommand">
         <parameter name="command"/>
         <body>
           <![CDATA[
             var controller = document.commandDispatcher.getControllerForCommand(command);

--- a/toolkit/content/widgets/tree.xml
+++ b/toolkit/content/widgets/tree.xml
@@ -1171,17 +1171,17 @@
               if (parentSelectable)
                 view.selection.select(parentIndex);
             }
           }
           this.parentNode.changeOpenState(cell.row);
           return;
         }
 
-        if (! view.selection.single) {
+        if (!view.selection.single) {
           var augment = this._isAccelPressed(event);
           if (event.shiftKey) {
             view.selection.rangedSelect(-1, cell.row, augment);
             b.ensureRowIsVisible(cell.row);
             return;
           }
           if (augment) {
             view.selection.toggleSelect(cell.row);

--- a/toolkit/identity/Identity.jsm
+++ b/toolkit/identity/Identity.jsm
@@ -270,17 +270,17 @@ IDService.prototype = {
       if (req.status < 200 || req.status >= 400) {
         log("_fetchWellKnownFile", url, ": server returned status:", req.status);
         return aCallback("Error");
       }
       try {
         let idpParams = req.response;
 
         // Verify that the IdP returned a valid configuration
-        if (! (idpParams.provisioning &&
+        if (!(idpParams.provisioning &&
             idpParams.authentication &&
             idpParams['public-key'])) {
           let errStr = "Invalid well-known file from: " + aDomain;
           log("_fetchWellKnownFile:", errStr);
           return aCallback(errStr);
         }
 
         let callbackObj = {

--- a/toolkit/identity/IdentityUtils.jsm
+++ b/toolkit/identity/IdentityUtils.jsm
@@ -48,17 +48,17 @@ this.checkRenamed = function checkRename
       defined(aOptions[aNewName])) {
     let err = "You cannot provide both " + aOldName + " and " + aNewName;
     Logger.reportError(err);
     throw new Error(err);
   }
 
   if (checkDeprecated(aOptions, aOldName)) {
     aOptions[aNewName] = aOptions[aOldName];
-    delete(aOptions[aOldName]);
+    delete aOptions[aOldName];
   }
 };
 
 this.getRandomId = function getRandomId() {
   return uuidgen.generateUUID().toString();
 };
 
 /*

--- a/toolkit/identity/RelyingParty.jsm
+++ b/toolkit/identity/RelyingParty.jsm
@@ -326,17 +326,17 @@ IdentityRelyingParty.prototype = {
    * @param aCallback
    *        (function) callback to invoke on completion
    *                   with first-positional parameter the error.
    */
   _generateAssertion: function _generateAssertion(aAudience, aIdentity, aCallback) {
     log("_generateAssertion: audience:", aAudience, "identity:", aIdentity);
 
     let id = this._store.fetchIdentity(aIdentity);
-    if (! (id && id.cert)) {
+    if (!(id && id.cert)) {
       let errStr = "Cannot generate an assertion without a certificate";
       log("ERROR: _generateAssertion:", errStr);
       aCallback(errStr);
       return;
     }
 
     let kp = id.keyPair;
 

--- a/toolkit/modules/InlineSpellChecker.jsm
+++ b/toolkit/modules/InlineSpellChecker.jsm
@@ -76,17 +76,17 @@ InlineSpellChecker.prototype = {
 
     var selcon = this.mEditor.selectionController;
     var spellsel = selcon.getSelection(selcon.SELECTION_SPELLCHECK);
     if (spellsel.rangeCount == 0)
       return; // easy case - no misspellings
 
     var range = this.mInlineSpellChecker.getMisspelledWord(rangeParent,
                                                           rangeOffset);
-    if (! range)
+    if (!range)
       return; // not over a misspelled word
 
     this.mMisspelling = range.toString();
     this.mOverMisspelling = true;
     this.mWordNode = rangeParent;
     this.mWordOffset = rangeOffset;
   },
 
@@ -145,19 +145,19 @@ InlineSpellChecker.prototype = {
         return 0;  // word seems not misspelled after all (?)
     } catch (e) {
         return 0;
     }
 
     this.mMenu = menu;
     this.mSpellSuggestions = [];
     this.mSuggestionItems = [];
-    for (var i = 0; i < maxNumber; i ++) {
+    for (var i = 0; i < maxNumber; i++) {
       var suggestion = spellchecker.GetSuggestedWord();
-      if (! suggestion.length)
+      if (!suggestion.length)
         break;
       this.mSpellSuggestions.push(suggestion);
 
       var item = menu.ownerDocument.createElement("menuitem");
       this.mSuggestionItems.push(item);
       item.setAttribute("label", suggestion);
       item.setAttribute("value", suggestion);
       // this function thing is necessary to generate a callback with the
@@ -169,25 +169,25 @@ InlineSpellChecker.prototype = {
     }
     return this.mSpellSuggestions.length;
   },
 
   // undoes the work of addSuggestionsToMenu for the same menu
   // (call from popup hiding)
   clearSuggestionsFromMenu: function()
   {
-    for (var i = 0; i < this.mSuggestionItems.length; i ++) {
+    for (var i = 0; i < this.mSuggestionItems.length; i++) {
       this.mMenu.removeChild(this.mSuggestionItems[i]);
     }
     this.mSuggestionItems = [];
   },
 
   sortDictionaryList: function(list) {
     var sortedList = [];
-    for (var i = 0; i < list.length; i ++) {
+    for (var i = 0; i < list.length; i++) {
       sortedList.push({"id": list[i],
                        "label": this.getDictionaryDisplayName(list[i])});
     }
     sortedList.sort(function(a, b) {
       if (a.label < b.label)
         return -1;
       if (a.label > b.label)
         return 1;
@@ -222,17 +222,17 @@ InlineSpellChecker.prototype = {
       var listcount = o2.value;
       try {
         curlang = spellchecker.GetCurrentDictionary();
       } catch (e) {}
     }
 
     var sortedList = this.sortDictionaryList(list);
 
-    for (var i = 0; i < sortedList.length; i ++) {
+    for (var i = 0; i < sortedList.length; i++) {
       this.mDictionaryNames.push(sortedList[i].id);
       var item = menu.ownerDocument.createElement("menuitem");
       item.setAttribute("id", "spell-check-dictionary-" + sortedList[i].id);
       item.setAttribute("label", sortedList[i].label);
       item.setAttribute("type", "radio");
       this.mDictionaryItems.push(item);
       if (curlang == sortedList[i].id) {
         item.setAttribute("checked", "true");
@@ -316,44 +316,44 @@ InlineSpellChecker.prototype = {
 
     return displayName;
   },
 
   // undoes the work of addDictionaryListToMenu for the menu
   // (call on popup hiding)
   clearDictionaryListFromMenu: function()
   {
-    for (var i = 0; i < this.mDictionaryItems.length; i ++) {
+    for (var i = 0; i < this.mDictionaryItems.length; i++) {
       this.mDictionaryMenu.removeChild(this.mDictionaryItems[i]);
     }
     this.mDictionaryItems = [];
   },
 
   // callback for selecting a dictionary
   selectDictionary: function(index)
   {
     if (this.mRemote) {
       this.mRemote.selectDictionary(index);
       return;
     }
-    if (! this.mInlineSpellChecker || index < 0 || index >= this.mDictionaryNames.length)
+    if (!this.mInlineSpellChecker || index < 0 || index >= this.mDictionaryNames.length)
       return;
     var spellchecker = this.mInlineSpellChecker.spellChecker;
     spellchecker.SetCurrentDictionary(this.mDictionaryNames[index]);
     this.mInlineSpellChecker.spellCheckRange(null); // causes recheck
   },
 
   // callback for selecting a suggested replacement
   replaceMisspelling: function(index)
   {
     if (this.mRemote) {
       this.mRemote.replaceMisspelling(index);
       return;
     }
-    if (! this.mInlineSpellChecker || ! this.mOverMisspelling)
+    if (!this.mInlineSpellChecker || !this.mOverMisspelling)
       return;
     if (index < 0 || index >= this.mSpellSuggestions.length)
       return;
     this.mInlineSpellChecker.replaceWord(this.mWordNode, this.mWordOffset,
                                          this.mSpellSuggestions[index]);
   },
 
   // callback for enabling or disabling spellchecking

--- a/toolkit/mozapps/extensions/internal/XPIProvider.jsm
+++ b/toolkit/mozapps/extensions/internal/XPIProvider.jsm
@@ -1947,17 +1947,17 @@ function removeAsync(aFile) {
     try {
       info = yield OS.File.stat(aFile.path);
       if (info.isDir)
         yield OS.File.removeDir(aFile.path);
       else
         yield OS.File.remove(aFile.path);
     }
     catch (e) {
-      if (!(e instanceof OS.File.Error) || ! e.becauseNoSuchFile)
+      if (!(e instanceof OS.File.Error) || !e.becauseNoSuchFile)
         throw e;
       // The file has already gone away
       return;
     }
   });
 }
 
 /**