diff --git a/package-lock.json b/package-lock.json
index d5e3e393ee3..a940f8399d6 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -5430,9 +5430,9 @@
       }
     },
     "text-buffer": {
-      "version": "13.14.6",
-      "resolved": "https://registry.npmjs.org/text-buffer/-/text-buffer-13.14.6.tgz",
-      "integrity": "sha512-CC2uyrnn+bZXIOVtXMR8jNPyrfciPGMjfyKBY9BkenbtQc06vHy9QvBhkDRf0kY/J1uCD3sJ/cbV6OV7yYM/Sw==",
+      "version": "13.14.8",
+      "resolved": "https://registry.npmjs.org/text-buffer/-/text-buffer-13.14.8.tgz",
+      "integrity": "sha512-hl2adF6WZf4fjy1AuIRZtPqRQ6in9V+KSM7I5eUp0FEI/PBH1EwaTzO1UWrnslI7Lybiiwx4TELOQXOVjFqfQg==",
       "requires": {
         "delegato": "^1.0.0",
         "diff": "^2.2.1",
diff --git a/package.json b/package.json
index d099b4cca64..60c096c87b6 100644
--- a/package.json
+++ b/package.json
@@ -157,7 +157,7 @@
     "symbols-view": "https://www.atom.io/api/packages/symbols-view/versions/0.118.2/tarball",
     "tabs": "https://www.atom.io/api/packages/tabs/versions/0.109.2/tarball",
     "temp": "^0.8.3",
-    "text-buffer": "13.14.6",
+    "text-buffer": "13.14.8",
     "timecop": "https://www.atom.io/api/packages/timecop/versions/0.36.2/tarball",
     "tree-sitter": "0.13.8",
     "tree-view": "https://www.atom.io/api/packages/tree-view/versions/0.224.2/tarball",
diff --git a/src/pane-axis.coffee b/src/pane-axis.coffee
deleted file mode 100644
index c8fcc4108aa..00000000000
--- a/src/pane-axis.coffee
+++ /dev/null
@@ -1,147 +0,0 @@
-{Emitter, CompositeDisposable} = require 'event-kit'
-{flatten} = require 'underscore-plus'
-Model = require './model'
-PaneAxisElement = require './pane-axis-element'
-
-module.exports =
-class PaneAxis extends Model
-  parent: null
-  container: null
-  orientation: null
-
-  @deserialize: (state, {deserializers, views}) ->
-    state.children = state.children.map (childState) ->
-      deserializers.deserialize(childState)
-    new this(state, views)
-
-  constructor: ({@orientation, children, flexScale}, @viewRegistry) ->
-    @emitter = new Emitter
-    @subscriptionsByChild = new WeakMap
-    @subscriptions = new CompositeDisposable
-    @children = []
-    if children?
-      @addChild(child) for child in children
-    @flexScale = flexScale ? 1
-
-  serialize: ->
-    deserializer: 'PaneAxis'
-    children: @children.map (child) -> child.serialize()
-    orientation: @orientation
-    flexScale: @flexScale
-
-  getElement: ->
-    @element ?= new PaneAxisElement().initialize(this, @viewRegistry)
-
-  getFlexScale: -> @flexScale
-
-  setFlexScale: (@flexScale) ->
-    @emitter.emit 'did-change-flex-scale', @flexScale
-    @flexScale
-
-  getParent: -> @parent
-
-  setParent: (@parent) -> @parent
-
-  getContainer: -> @container
-
-  setContainer: (container) ->
-    if container and container isnt @container
-      @container = container
-      child.setContainer(container) for child in @children
-
-  getOrientation: -> @orientation
-
-  getChildren: -> @children.slice()
-
-  getPanes: ->
-    flatten(@children.map (child) -> child.getPanes())
-
-  getItems: ->
-    flatten(@children.map (child) -> child.getItems())
-
-  onDidAddChild: (fn) ->
-    @emitter.on 'did-add-child', fn
-
-  onDidRemoveChild: (fn) ->
-    @emitter.on 'did-remove-child', fn
-
-  onDidReplaceChild: (fn) ->
-    @emitter.on 'did-replace-child', fn
-
-  onDidDestroy: (fn) ->
-    @emitter.once 'did-destroy', fn
-
-  onDidChangeFlexScale: (fn) ->
-    @emitter.on 'did-change-flex-scale', fn
-
-  observeFlexScale: (fn) ->
-    fn(@flexScale)
-    @onDidChangeFlexScale(fn)
-
-  addChild: (child, index=@children.length) ->
-    @children.splice(index, 0, child)
-    child.setParent(this)
-    child.setContainer(@container)
-    @subscribeToChild(child)
-    @emitter.emit 'did-add-child', {child, index}
-
-  adjustFlexScale: ->
-    # get current total flex scale of children
-    total = 0
-    total += child.getFlexScale() for child in @children
-
-    needTotal = @children.length
-    # set every child's flex scale by the ratio
-    for child in @children
-      child.setFlexScale(needTotal * child.getFlexScale() / total)
-
-  removeChild: (child, replacing=false) ->
-    index = @children.indexOf(child)
-    throw new Error("Removing non-existent child") if index is -1
-
-    @unsubscribeFromChild(child)
-
-    @children.splice(index, 1)
-    @adjustFlexScale()
-    @emitter.emit 'did-remove-child', {child, index}
-    @reparentLastChild() if not replacing and @children.length < 2
-
-  replaceChild: (oldChild, newChild) ->
-    @unsubscribeFromChild(oldChild)
-    @subscribeToChild(newChild)
-
-    newChild.setParent(this)
-    newChild.setContainer(@container)
-
-    index = @children.indexOf(oldChild)
-    @children.splice(index, 1, newChild)
-    @emitter.emit 'did-replace-child', {oldChild, newChild, index}
-
-  insertChildBefore: (currentChild, newChild) ->
-    index = @children.indexOf(currentChild)
-    @addChild(newChild, index)
-
-  insertChildAfter: (currentChild, newChild) ->
-    index = @children.indexOf(currentChild)
-    @addChild(newChild, index + 1)
-
-  reparentLastChild: ->
-    lastChild = @children[0]
-    lastChild.setFlexScale(@flexScale)
-    @parent.replaceChild(this, lastChild)
-    @destroy()
-
-  subscribeToChild: (child) ->
-    subscription = child.onDidDestroy => @removeChild(child)
-    @subscriptionsByChild.set(child, subscription)
-    @subscriptions.add(subscription)
-
-  unsubscribeFromChild: (child) ->
-    subscription = @subscriptionsByChild.get(child)
-    @subscriptions.remove(subscription)
-    subscription.dispose()
-
-  destroyed: ->
-    @subscriptions.dispose()
-    @emitter.emit 'did-destroy'
-    @emitter.dispose()
diff --git a/src/pane-axis.js b/src/pane-axis.js
new file mode 100644
index 00000000000..23c87f9283e
--- /dev/null
+++ b/src/pane-axis.js
@@ -0,0 +1,199 @@
+const {Emitter, CompositeDisposable} = require('event-kit')
+const {flatten} = require('underscore-plus')
+const Model = require('./model')
+const PaneAxisElement = require('./pane-axis-element')
+
+class PaneAxis extends Model {
+  static deserialize (state, {deserializers, views}) {
+    state.children = state.children.map(childState => deserializers.deserialize(childState))
+    return new PaneAxis(state, views)
+  }
+
+  constructor ({orientation, children, flexScale}, viewRegistry) {
+    super()
+    this.parent = null
+    this.container = null
+    this.orientation = orientation
+    this.viewRegistry = viewRegistry
+    this.emitter = new Emitter()
+    this.subscriptionsByChild = new WeakMap()
+    this.subscriptions = new CompositeDisposable()
+    this.flexScale = flexScale != null ? flexScale : 1
+    this.children = []
+    if (children) {
+      for (let child of children) {
+        this.addChild(child)
+      }
+    }
+  }
+
+  serialize () {
+    return {
+      deserializer: 'PaneAxis',
+      children: this.children.map(child => child.serialize()),
+      orientation: this.orientation,
+      flexScale: this.flexScale
+    }
+  }
+
+  getElement () {
+    if (!this.element) {
+      this.element = new PaneAxisElement().initialize(this, this.viewRegistry)
+    }
+    return this.element
+  }
+
+  getFlexScale () {
+    return this.flexScale
+  }
+
+  setFlexScale (flexScale) {
+    this.flexScale = flexScale
+    this.emitter.emit('did-change-flex-scale', this.flexScale)
+    return this.flexScale
+  }
+
+  getParent () {
+    return this.parent
+  }
+
+  setParent (parent) {
+    this.parent = parent
+    return this.parent
+  }
+
+  getContainer () {
+    return this.container
+  }
+
+  setContainer (container) {
+    if (container && (container !== this.container)) {
+      this.container = container
+      this.children.forEach(child => child.setContainer(container))
+    }
+  }
+
+  getOrientation () {
+    return this.orientation
+  }
+
+  getChildren () {
+    return this.children.slice()
+  }
+
+  getPanes () {
+    return flatten(this.children.map(child => child.getPanes()))
+  }
+
+  getItems () {
+    return flatten(this.children.map(child => child.getItems()))
+  }
+
+  onDidAddChild (fn) {
+    return this.emitter.on('did-add-child', fn)
+  }
+
+  onDidRemoveChild (fn) {
+    return this.emitter.on('did-remove-child', fn)
+  }
+
+  onDidReplaceChild (fn) {
+    return this.emitter.on('did-replace-child', fn)
+  }
+
+  onDidDestroy (fn) {
+    return this.emitter.once('did-destroy', fn)
+  }
+
+  onDidChangeFlexScale (fn) {
+    return this.emitter.on('did-change-flex-scale', fn)
+  }
+
+  observeFlexScale (fn) {
+    fn(this.flexScale)
+    return this.onDidChangeFlexScale(fn)
+  }
+
+  addChild (child, index = this.children.length) {
+    this.children.splice(index, 0, child)
+    child.setParent(this)
+    child.setContainer(this.container)
+    this.subscribeToChild(child)
+    return this.emitter.emit('did-add-child', {child, index})
+  }
+
+  adjustFlexScale () {
+    // get current total flex scale of children
+    let total = 0
+    for (var child of this.children) { total += child.getFlexScale() }
+
+    const needTotal = this.children.length
+    // set every child's flex scale by the ratio
+    for (child of this.children) {
+      child.setFlexScale((needTotal * child.getFlexScale()) / total)
+    }
+  }
+
+  removeChild (child, replacing = false) {
+    const index = this.children.indexOf(child)
+    if (index === -1) { throw new Error('Removing non-existent child') }
+
+    this.unsubscribeFromChild(child)
+
+    this.children.splice(index, 1)
+    this.adjustFlexScale()
+    this.emitter.emit('did-remove-child', {child, index})
+    if (!replacing && this.children.length < 2) {
+      this.reparentLastChild()
+    }
+  }
+
+  replaceChild (oldChild, newChild) {
+    this.unsubscribeFromChild(oldChild)
+    this.subscribeToChild(newChild)
+
+    newChild.setParent(this)
+    newChild.setContainer(this.container)
+
+    const index = this.children.indexOf(oldChild)
+    this.children.splice(index, 1, newChild)
+    this.emitter.emit('did-replace-child', {oldChild, newChild, index})
+  }
+
+  insertChildBefore (currentChild, newChild) {
+    const index = this.children.indexOf(currentChild)
+    return this.addChild(newChild, index)
+  }
+
+  insertChildAfter (currentChild, newChild) {
+    const index = this.children.indexOf(currentChild)
+    return this.addChild(newChild, index + 1)
+  }
+
+  reparentLastChild () {
+    const lastChild = this.children[0]
+    lastChild.setFlexScale(this.flexScale)
+    this.parent.replaceChild(this, lastChild)
+    this.destroy()
+  }
+
+  subscribeToChild (child) {
+    const subscription = child.onDidDestroy(() => this.removeChild(child))
+    this.subscriptionsByChild.set(child, subscription)
+    this.subscriptions.add(subscription)
+  }
+
+  unsubscribeFromChild (child) {
+    const subscription = this.subscriptionsByChild.get(child)
+    this.subscriptions.remove(subscription)
+    subscription.dispose()
+  }
+
+  destroyed () {
+    this.subscriptions.dispose()
+    this.emitter.emit('did-destroy')
+    this.emitter.dispose()
+  }
+}
+
+module.exports = PaneAxis