Functional Programming - Understand the Hazards of Using Imperative Code

Tell us what’s happening: the code does not give the correct uoutput, can someone plz help.

Describe your issue in detail here.
final tab output give error(debug does not help).

Your code so far

// tabs is an array of titles of each site open within the window
const Window = function(tabs) {
  this.tabs = tabs; // We keep a record of the array inside the object

// When you join two windows into one window
Window.prototype.join = function(otherWindow) {
  this.tabs = this.tabs.concat(otherWindow.tabs);
  return this;

// When you open a new tab at the end
Window.prototype.tabOpen = function(tab) {
  this.tabs.push('new tab'); // Let's open a new tab for now
  return this;

// When you close a tab
Window.prototype.tabClose = function(index) {

  // Only change code below this line

const tabsBeforeIndex = this.tabs.slice(0, index); // Get the tabs before the tab
  const tabsAfterIndex = this.tabs.slice(index + 1); // Get the tabs after the tab

  this.tabs = tabsBeforeIndex.concat(tabsBeforeIndex,tabsAfterIndex); // Join them together

  // Only change code above this line

  return this;

// Let's create three browser windows
const workWindow = new Window(['GMail', 'Inbox', 'Work mail', 'Docs', 'freeCodeCamp']); // Your mailbox, drive, and other work sites
const socialWindow = new Window(['FB', 'Gitter', 'Reddit', 'Twitter', 'Medium']); // Social sites
const videoWindow = new Window(['Netflix', 'YouTube', 'Vimeo', 'Vine']); // Entertainment sites

// Now perform the tab opening, closing, and other operations
const finalTabs = socialWindow
  .tabOpen() // Open a new tab for cat memes
  .join(videoWindow.tabClose(2)) // Close third tab in video window, and join

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/ Safari/537.36

Challenge Information:

Functional Programming - Understand the Hazards of Using Imperative Code

You appear to have created this post without editing the template. Please edit your post to Tell us what’s happening in your own words.

Welcome to the forum @thibok51811

The .slice method is for copying, is this what you want to do?

Your code is concatenating tabsBeforeIndex onto itself.
This will create a duplicate.

Happy coding