Extract sort array function

app/javascript/src/classes/thumbnail_view.coffee

@@ -1,3 +1,4 @@
+import { sortArrayByDistance } from '../utils/array'
 import PreloadContainer from './preload_container'
 
 # Handle the thumbnail view, and navigation for the main view.
@@ -161,7 +162,7 @@ export default class ThumbnailView
       # centered on.  If that doesn't match, move outwards from there.  Only look forward
       # a little bit, or we may match a post that was never seen and jump forward too far
       # in the results.
-      post_id_search_order = sort_array_by_distance(old_post_ids.slice(0, old_centered_post_idx + 3), old_centered_post_idx)
+      post_id_search_order = sortArrayByDistance(old_post_ids.slice(0, old_centered_post_idx + 3), old_centered_post_idx)
       initial_post_id = null
       i = 0
       while i < post_id_search_order.length

app/javascript/src/utils/array.js

@@ -1,21 +1,27 @@
-###
-# Return the values of list starting at idx and moving outwards.
-#
-# sort_array_by_distance([0,1,2,3,4,5,6,7,8,9], 5)
-# [5,4,6,3,7,2,8,1,9,0]
-###
+/**
+ * Return the values of list starting at idx and moving outwards.
+ *
+ * sort_array_by_distance([0,1,2,3,4,5,6,7,8,9], 5)
+ * [5,4,6,3,7,2,8,1,9,0]
+ */
+export function sortArrayByDistance (list, idx) {
+  const ret = [list[idx]];
 
-window.sort_array_by_distance = (list, idx) ->
-  ret = []
-  ret.push list[idx]
-  distance = 1
-  loop
-    length = ret.length
-    if idx - distance >= 0
-      ret.push list[idx - distance]
-    if idx + distance < list.length
-      ret.push list[idx + distance]
-    if length == ret.length
-      break
-    ++distance
-  ret
+  for (let distance = 1; ; ++distance) {
+    const length = ret.length;
+
+    if (idx - distance >= 0) {
+      ret.push(list[idx - distance]);
+    }
+
+    if (idx + distance < list.length) {
+      ret.push(list[idx + distance]);
+    }
+
+    if (length === ret.length) {
+      break;
+    }
+  }
+
+  return ret;
+}