[array/bubblesortItem] fix edge case

Author: dmonad

array.js

@@ -205,13 +205,13 @@ export const bubblesortItem = (arr, i, compareFn) => {
   const n = arr[i]
   let j = i
   // try to sort to the right
-  while (compareFn(n, arr[j + 1]) > 0) {
+  while (j + 1 < arr.length && compareFn(n, arr[j + 1]) > 0) {
     arr[j] = arr[j + 1]
     arr[++j] = n
   }
   if (i === j && j > 0) { // no change yet
     // sort to the left
-    while (compareFn(arr[j - 1], n) > 0) {
+    while (j > 0 && compareFn(arr[j - 1], n) > 0) {
       arr[j] = arr[j - 1]
       arr[--j] = n
     }

array.test.js

@@ -119,6 +119,16 @@ export const testUnique = _tc => {
   t.compare([], array.uniqueBy([], o => o))
 }
 
+/**
+ * @param {t.TestCase} tc
+ */
+export const testBubblesortItemEdgeCases = tc => {
+  // does not throw..
+  array.bubblesortItem([1], 0, (a, b) => a - b)
+  array.bubblesortItem([2, 1], 1, (a, b) => a - b)
+  array.bubblesortItem([2, 1], 0, (a, b) => a - b)
+}
+
 /**
  * @param {t.TestCase} tc
  */