diff --git a/emacs/.emacs.d/GNUmakefile b/emacs/.emacs.d/GNUmakefile
index a6b3f25..83b9876 100644
--- a/emacs/.emacs.d/GNUmakefile
+++ b/emacs/.emacs.d/GNUmakefile
@@ -5,13 +5,14 @@ include ../../dotfiles.mk
 AUTOLOADS_FILE = site-lisp/site-autoloads.el
 UNWANTED = $(AUTOLOADS_FILE) site-lisp/flycheck_% site-lisp/flycheck-%
 SITE_LISPS = $(addsuffix c,$(filter-out $(UNWANTED),$(wildcard site-lisp/*.el)))
-INIT_LISPS = init/oni-org-init.elc $(addsuffix .elc,$(basename $(wildcard init/*.org)))
+INIT_LISPS = init/oni-org-init.elc init/oni-js2-init.elc \
+    $(addsuffix .elc,$(basename $(wildcard init/*.org)))
 VENDOR_DIRS = $(wildcard vendor-lisp/*)
 
 .PHONE: all snippets
 all: $(SITE_LISPS) init.elc $(INIT_LISPS) $(AUTOLOADS_FILE) snippets
 
-init.el init/oni-org-init.el: init.org
+init.el init/oni-org-init.el init/oni-js2-init.el: init.org
 	$(call tangle,emacs-lisp)
 
 %.el: %.org
diff --git a/emacs/.emacs.d/init.org b/emacs/.emacs.d/init.org
index 9b311b9..74ab5f5 100644
--- a/emacs/.emacs.d/init.org
+++ b/emacs/.emacs.d/init.org
@@ -195,6 +195,15 @@ Computing Environment".
        (setq auto-save-list-file-prefix (oni:data-location "auto-save-list/.saves-"))
      #+END_SRC
 
+*** Additional file type mappings
+
+    Load =*.js= files with [[JavaScript IDE mode]]. ~js2-mode~ is a better
+    JavaScript mode than plain old ~js-mode~.
+
+    #+BEGIN_SRC emacs-lisp
+      (add-to-list 'auto-mode-alist '("\\.js\\'" . js2-mode))
+    #+END_SRC
+
 * Typographic style
 
   Emacs being a text editor has options on how to handle your text.
@@ -1134,6 +1143,35 @@ Computing Environment".
      (add-hook 'lisp-mode-hook 'company-mode)
    #+END_SRC
 
+** JavaScript IDE mode
+   :PROPERTIES:
+   :header-args: :tangle "init/oni-js2-init.el"
+   :END:
+
+  Since ~js2-mode~ isn't loaded when Emacs starts put the
+  configuration in a different file so that it doesn't cause a
+  slowdown in startup time.
+
+  #+BEGIN_SRC emacs-lisp :tangle yes
+    (with-eval-after-load 'js2-mode (load "oni-js2-init"))
+  #+END_SRC
+
+  Keep the byte-compiler happy by requiring ~js2-mode~, by this time
+  it will have been loaded anyway.
+
+  #+BEGIN_SRC emacs-lisp
+    (require 'js2-mode)
+  #+END_SRC
+
+  Silence warnings about trailing commas in JavaScript code. I usually
+  write code that goes through Babel or something similar and doesn't
+  actually die when a trailing comma is present. Also this should
+  really be handled by a linter such as eslint.
+
+  #+BEGIN_SRC emacs-lisp
+    (setq js2-strict-trailing-comma-warning nil)
+  #+END_SRC
+
 * Applications
 
   - [[file:init/dired-init.org][Dired]] :: The Emacs file manager. Very powerful, and I don't use it