diff --git a/package.json b/package.json
index 7c43bca47..85ae14ef0 100644
--- a/package.json
+++ b/package.json
@@ -26,13 +26,13 @@
     "grunt-bump": "~0.0.13",
     "grunt-concurrent": "~0.4.3",
     "grunt-contrib-clean": "~0.5.0",
-    "grunt-contrib-coffee": "~0.8.2",
+    "grunt-contrib-coffee": "~0.9.0",
     "grunt-contrib-compress": "~0.6.0",
     "grunt-contrib-concat": "~0.3.0",
     "grunt-contrib-copy": "~0.5.0",
     "grunt-contrib-watch": "~0.5.3",
     "grunt-shell": "~0.6.4",
-    "load-grunt-tasks": "~0.2.1"
+    "load-grunt-tasks": "~0.3.0"
   },
   "repository": {
     "type": "git",
diff --git a/src/General/Build.coffee b/src/General/Build.coffee
index 1a3efa7ed..f342857af 100644
--- a/src/General/Build.coffee
+++ b/src/General/Build.coffee
@@ -176,7 +176,7 @@ Build =
       ''
 
     if isOP and g.VIEW is 'index'
-      pageNum   = Math.floor Index.liveThreadIDs.indexOf(postID) / Index.threadsNumPerPage
+      pageNum   = Index.liveThreadIDs.indexOf(postID) // Index.threadsNumPerPage
       pageIcon  = " <span class=page-num title='This thread is on page #{pageNum} in the original index.'>Page #{pageNum}</span>"
       replyLink = " &nbsp; <span>[<a href='/#{boardID}/res/#{threadID}' class=replylink>Reply</a>]</span>"
     else
@@ -284,7 +284,7 @@ Build =
 
     postCount = data.replies + 1
     fileCount = data.images  + !!data.ext
-    pageCount = Math.floor Index.liveThreadIDs.indexOf(thread.ID) / Index.threadsNumPerPage
+    pageCount = Index.liveThreadIDs.indexOf(thread.ID) // Index.threadsNumPerPage
 
     subject = if thread.OP.info.subject
       "<div class='subject'>#{thread.OP.info.subject}</div>"
diff --git a/src/General/Get.coffee b/src/General/Get.coffee
index 9fe328a13..d05651789 100644
--- a/src/General/Get.coffee
+++ b/src/General/Get.coffee
@@ -188,7 +188,7 @@ Get =
 
     comment = bq.innerHTML
       # greentext
-      .replace(/(^|>)(&gt;[^<$]*)(<|$)/g, '$1<span class=quote>$2</span>$3')
+      .replace /(^|>)(&gt;[^<$]*)(<|$)/g, '$1<span class=quote>$2</span>$3'
       # quotes
       .replace /((&gt;){2}(&gt;\/[a-z\d]+\/)?\d+)/g, '<span class=deadlink>$1</span>'
 
diff --git a/src/General/Index.coffee b/src/General/Index.coffee
index 1ce167006..5c6cc8919 100644
--- a/src/General/Index.coffee
+++ b/src/General/Index.coffee
@@ -344,7 +344,7 @@ Index =
       threadRoot = Build.thread g.BOARD, threadData
       Index.nodes.push threadRoot, $.el 'hr'
       if thread = g.BOARD.threads[threadData.no]
-        thread.setPage Math.floor i / Index.threadsNumPerPage
+        thread.setPage i // Index.threadsNumPerPage
         thread.setCount 'post', threadData.replies + 1,                threadData.bumplimit
         thread.setCount 'file', threadData.images  + !!threadData.ext, threadData.imagelimit
         thread.setStatus 'Sticky', !!threadData.sticky
@@ -394,8 +394,8 @@ Index =
     Main.callbackNodes Post, posts
   buildCatalogViews: ->
     threads = Index.sortedNodes
-      .filter((n, i) -> !(i % 2))
-      .map((threadRoot) -> Get.threadFromRoot threadRoot)
+      .filter (n, i) -> !(i % 2)
+      .map (threadRoot) -> Get.threadFromRoot threadRoot
       .filter (thread) -> !thread.isHidden
     catalogThreads = []
     for thread in threads when !thread.catalogView
@@ -408,8 +408,8 @@ Index =
         sortedThreadIDs = Index.liveThreadIDs
       when 'lastreply'
         sortedThreadIDs = [Index.liveThreadData...].sort((a, b) ->
-          a = a.last_replies[a.last_replies.length - 1] if 'last_replies' of a
-          b = b.last_replies[b.last_replies.length - 1] if 'last_replies' of b
+          [..., a] = a.last_replies if 'last_replies' of a
+          [..., b] = b.last_replies if 'last_replies' of b
           b.no - a.no
         ).map (data) -> data.no
       when 'birth'
diff --git a/src/General/UI.coffee b/src/General/UI.coffee
index e52774aea..ee852ccd4 100644
--- a/src/General/UI.coffee
+++ b/src/General/UI.coffee
@@ -191,7 +191,7 @@ UI = do ->
     # prevent text selection
     e.preventDefault()
     if isTouching = e.type is 'touchstart'
-      e = e.changedTouches[e.changedTouches.length - 1]
+      [..., e] = e.changedTouches
     # distance from pointer to el edge is constant; calculate it here.
     el = $.x 'ancestor::div[contains(@class,"dialog")][1]', @
     rect = el.getBoundingClientRect()
diff --git a/src/Posting/QR.cooldown.coffee b/src/Posting/QR.cooldown.coffee
index ce0fa7960..e6dd14a8d 100644
--- a/src/Posting/QR.cooldown.coffee
+++ b/src/Posting/QR.cooldown.coffee
@@ -76,7 +76,7 @@ QR.cooldown =
       if isReply is cooldown.isReply
         # Only cooldowns relevant to this post can set the seconds variable:
         #   reply cooldown with a reply, thread cooldown with a thread
-        elapsed = Math.floor (now - start) / $.SECOND
+        elapsed = (now - start) // $.SECOND
         continue if elapsed < 0 # clock changed since then?
         type = unless isReply
           'thread'
@@ -91,7 +91,7 @@ QR.cooldown =
         seconds = Math.max seconds, types[type] - elapsed
 
     if seconds and Conf['Cooldown Prediction'] and hasFile and upSpd
-      seconds -= Math.floor post.file.size / upSpd * upSpdAccuracy
+      seconds -= post.file.size // (upSpd * upSpdAccuracy)
       seconds  = Math.max seconds, 0
     # Update the status when we change posting type.
     # Don't get stuck at some random number.
diff --git a/src/Posting/QR.post.coffee b/src/Posting/QR.post.coffee
index 06194bbe3..a38362840 100644
--- a/src/Posting/QR.post.coffee
+++ b/src/Posting/QR.post.coffee
@@ -35,7 +35,7 @@ QR.post = class
     else
       'new'
 
-    prev = QR.posts[QR.posts.length - 1]
+    [..., prev] = QR.posts
     QR.posts.push @
     @nodes.spoiler.checked = @spoiler = if prev and Conf['Remember Spoiler']
       prev.spoiler