fix: Off by one error in next/previous tab

.vscode/settings.json

@@ -23,4 +23,7 @@
       "autoFix": true
     },
   ],
+  "editor.codeActionsOnSave": {
+    "source.fixAll.eslint": true
+  },
 }

cypress/integration/spec.js

@@ -1,4 +1,5 @@
 /// <reference types="cypress"/>
+/* global cy */
 
 // const { _ } = Cypress
 
@@ -93,6 +94,16 @@ describe('form test', () => {
     cy.get('body').should(beFocused)
   })
 
+  it('moves focus back to the first element when the last element is focused', () => {
+    cy.get('a:last').tab()
+    cy.get('a:first').should(beFocused)
+  })
+
+  it('moves focus back to the first element when the last element is focused', () => {
+    cy.get('a:first').tab({ shift: true })
+    cy.get('a:last').should(beFocused)
+  })
+
   describe('events', () => {
     beforeEach(() => {
 

src/index.js

@@ -1,3 +1,4 @@
+/* global Cypress, cy */
 const tabSequence = require('ally.js/query/tabsequence')
 
 const { _, Promise } = Cypress
@@ -75,22 +76,14 @@ const performTab = (el, options) => {
 
 const nextItemFromIndex = (i, seq, reverse) => {
   if (reverse) {
-    if (i === 0 || i === -1) {
-      i = seq.length
-    }
-  } else {
-    if (i === seq.length) {
-      i = 0
-    }
+    const nextIndex = i <= 0 ? seq.length - 1 : i - 1
 
+    return seq[nextIndex]
   }
-  // }
 
-  if (reverse) {
-    return seq[i - 1]
-  }
+  const nextIndex = i === seq.length - 1 ? 0 : i + 1
 
-  return seq[i + 1]
+  return seq[nextIndex]
 }
 
 const tabKeyEventPartial = {