Run decaffeinate on action_cable/*.js

Using [decaffeinate], we have converted these files from coffeescript
syntax to ES2015 syntax. Decaffeinate is very conservative in the
conversion process to ensure exact coffeescript semantics are preserved.
Most of the time, it's safe to clean up the code, and decaffeinate has
left suggestions regarding potential cleanups we can take. I'll tackle
those cleanups separately.

After running decaffeinate, I ran:
```
eslint --fix app/javascript
```
using the eslint configuration from ActiveStorage to automatically
correct lint violations in the decaffeinated output. This removed 189
extra semicolons and changed one instance of single quotes to double
quotes.

Note: decaffeinate and eslint can't parse ERB syntax. So I worked around
that by temporarily quoting the ERB:
```diff
 @ActionCable =
-  INTERNAL: <%= ActionCable::INTERNAL.to_json %>
+  INTERNAL: "<%= ActionCable::INTERNAL.to_json %>"
   WebSocket: window.WebSocket
   logger: window.console
```
and then removing those quotes after running decaffeinate and eslint.

[decaffeinate]: https://github.com/decaffeinate/decaffeinate

1 files changed, 46 insertions, 27 deletions

diff --git a/actioncable/app/javascript/action_cable/index.js.erb b/actioncable/app/javascript/action_cable/index.js.erb
index e0758dae72..a5fb5b4556 100644
--- a/actioncable/app/javascript/action_cable/index.js.erb
+++ b/actioncable/app/javascript/action_cable/index.js.erb
@@ -1,38 +1,57 @@
-#= export ActionCable
-#= require_self
-#= require ./action_cable/consumer
+/*
+ * decaffeinate suggestions:
+ * DS101: Remove unnecessary use of Array.from
+ * DS102: Remove unnecessary code created because of implicit returns
+ * DS104: Avoid inline assignments
+ * DS207: Consider shorter variations of null checks
+ * DS208: Avoid top-level this
+ * Full docs: https://github.com/decaffeinate/decaffeinate/blob/master/docs/suggestions.md
+ */
+//= export ActionCable
+//= require_self
+//= require ./action_cable/consumer
 
-@ActionCable =
-  INTERNAL: <%= ActionCable::INTERNAL.to_json %>
-  WebSocket: window.WebSocket
-  logger: window.console
+this.ActionCable = {
+  INTERNAL: <%= ActionCable::INTERNAL.to_json %>,
+  WebSocket: window.WebSocket,
+  logger: window.console,
 
-  createConsumer: (url) ->
-    url ?= @getConfig("url") ? @INTERNAL.default_mount_path
-    new ActionCable.Consumer @createWebSocketURL(url)
+  createConsumer(url) {
+    if (url == null) { let left
+    url = (left = this.getConfig("url")) != null ? left : this.INTERNAL.default_mount_path }
+    return new ActionCable.Consumer(this.createWebSocketURL(url))
+  },
 
-  getConfig: (name) ->
-    element = document.head.querySelector("meta[name='action-cable-#{name}']")
-    element?.getAttribute("content")
+  getConfig(name) {
+    const element = document.head.querySelector(`meta[name='action-cable-${name}']`)
+    return (element != null ? element.getAttribute("content") : undefined)
+  },
 
-  createWebSocketURL: (url) ->
-    if url and not /^wss?:/i.test(url)
-      a = document.createElement("a")
+  createWebSocketURL(url) {
+    if (url && !/^wss?:/i.test(url)) {
+      const a = document.createElement("a")
       a.href = url
-      # Fix populating Location properties in IE. Otherwise, protocol will be blank.
+      // Fix populating Location properties in IE. Otherwise, protocol will be blank.
       a.href = a.href
       a.protocol = a.protocol.replace("http", "ws")
-      a.href
-    else
-      url
+      return a.href
+    } else {
+      return url
+    }
+  },
 
-  startDebugging: ->
-    @debugging = true
+  startDebugging() {
+    return this.debugging = true
+  },
 
-  stopDebugging: ->
-    @debugging = null
+  stopDebugging() {
+    return this.debugging = null
+  },
 
-  log: (messages...) ->
-    if @debugging
+  log(...messages) {
+    if (this.debugging) {
       messages.push(Date.now())
-      @logger.log("[ActionCable]", messages...)
+      return this.logger.log("[ActionCable]", ...Array.from(messages))
+    }
+  }
+}