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HTML 

              
                 <div class="popup">
      <div class="content">
        <h1 class="title-text">Add New Task</h1>
        <div class="input-container">
          <input class="new-task-input" type="text" />
        </div>
        <div class="btn-container">
          <a class="btn add-new-task-button disabled">ADD</a>
        </div>
      </div>
      <span class="close-btn">
        <img src="https://jssecrets.com/wp-content/uploads/2023/02/cross.svg" alt="close btn" />
      </span>
    </div>

    <div class="overlay"></div>
    <!-- ------------END popup-------------- -->

    <!-- tasks list -->
    <div class="tasks-list-container">
      <h1 class="tasks-list-title">Active tasks</h1>
      <ul class="tasks-list"></ul>
      <div class="add-new-task-container">
        <button class="plus-button hello">
          <img src="https://jssecrets.com/wp-content/uploads/2023/02/plus.svg" alt="add button" />
        </button>
      </div>
    </div>
    <!--END tasks list -->

    <!-- tabs -->
    <div class="tasks-list-settings">
      <ul class="tabs">
        <li class="tab active showActive">
          <span class="title">Active</span>
        </li>
        <li class="tab showCompleted">
          <span class="title">Completed</span>
        </li>
        <div class="slider"></div>
      </ul>
    </div>
    <!--END tabs -->

    <!-- made in jssecrets.com -->
    <a class="jssecrets" href="https://jssecrets.com/" target="_blank"
      >jssecrets.com</a
    >
    <!-- made in jssecrets.com -->
!

CSS 

              
                @import url("https://fonts.googleapis.com/css2?family=Poppins:wght@400;500;800&display=swap");
@import url("https://fonts.googleapis.com/css2?family=Urbanist:wght@500&display=swap");
*,
::before,
::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: "Poppins", sans-serif;
}

ul {
  list-style: none;
}

.btn {
  padding: 16px 32px;
  font-size: 1em;
  border: none;
  outline: none;
  cursor: pointer;
  text-align: center;
  border-radius: 9px;
  position: relative;
  transition: all 0.2s linear;
}

body {
  height: 100vh;
  background: hsl(225deg, 14%, 12%);
  position: relative;
  overflow: hidden;
  color: #292d34;
}

.tasks-list-title {
  text-align: center;
  margin-bottom: 40px;
  color: white;
  font-size: 32px;
}
@media (max-width: 320px) {
  .tasks-list-title {
    font-size: 24px;
  }
}

.tasks-list-container {
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  opacity: 1;
  transition: all 0.7s ease-out;
}

.tasks-list {
  width: 480px;
  margin-left: auto;
  margin-right: auto;
  border-radius: 10px;
  background-color: hsl(225deg, 14%, 17%);
  border: 1.5px solid rgba(0, 0, 0, 0.38);
  box-shadow: 0 8px 32px 0 hsl(225deg, 14%, 12%);
  backdrop-filter: blur(40px);
  padding: 24px;
}
@media (max-width: 575px) {
  .tasks-list {
    width: 400px;
    padding: 16px;
  }
}
@media (max-width: 440px) {
  .tasks-list {
    width: 360px;
    padding: 12px;
  }
}
@media (max-width: 400px) {
  .tasks-list {
    width: 300px;
  }
}
@media (max-width: 400px) {
  .tasks-list {
    width: 240px;
    padding: 8px;
  }
}
.tasks-list .task {
  width: 100%;
  padding: 16px;
  border-radius: 16px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  transition: all 0.5s ease-out;
  background-color: hsl(225deg, 14%, 22%);
  backdrop-filter: blur(40px);
  border: 1px solid rgba(0, 0, 0, 0.33);
  box-shadow: 0 8px 32px 0 hsl(225deg, 14%, 12%);
}
@media (max-width: 320px) {
  .tasks-list .task {
    padding: 8px;
  }
}
.tasks-list .task:not(:first-of-type) {
  margin-top: 16px;
}
.tasks-list .task.completed {
  display: none;
}
.tasks-list .task .complete-task {
  display: block;
  width: 28px;
  height: 28px;
  min-width: 28px;
  border-radius: 50%;
  background-color: transparent;
  border: 2px solid #56d0f5;
  box-shadow: 0 0 12px rgba(86, 208, 245, 0.5);
  cursor: pointer;
}
.tasks-list .task .complete-task.no-border {
  border: none;
}
.tasks-list .task .complete-task.empty {
  border: 2px solid #56d0f5;
}
.tasks-list .task .complete-task.empty .checkmark {
  opacity: 0;
  visibility: hidden;
}
.tasks-list .task .complete-task .checkmark {
  vertical-align: middle;
  fill-rule: evenodd;
  clip-rule: evenodd;
  stroke-linejoin: round;
  stroke-miterlimit: 10;
  box-shadow: inset 0px 0px 0px #56d0f5;
  border-radius: 50%;
  background-color: transparent;
  pointer-events: none;
}
.tasks-list .task .complete-task .checkmark * {
  fill: transparent;
  stroke: transparent;
}
.tasks-list .task .complete-task .checkmark.animated {
  animation: fill-checkmark 0.4s ease-in-out 0.4s forwards, scale 0.3s ease-in-out 0.9s both;
}
.tasks-list .task .complete-task .checkmark.animated .circle {
  fill: none;
  stroke-width: 2;
  stroke-miterlimit: 10;
  stroke: #56d0f5;
  stroke-dasharray: 79;
  stroke-dashoffset: 79;
  animation: stroke 0.6s cubic-bezier(0.65, 0, 0.45, 1) forwards;
}
.tasks-list .task .complete-task .checkmark.animated .check {
  fill: none;
  fill-rule: nonzero;
  stroke: #fff;
  stroke-width: 2.5px;
  stroke-dasharray: 23;
  stroke-dashoffset: 23;
  animation: stroke 0.3s cubic-bezier(0.65, 0, 0.45, 1) 0.8s forwards;
}
.tasks-list .task .delete-task {
  display: block;
  width: 28px;
  height: 28px;
  min-width: 28px;
  border-radius: 50%;
  border: 2px solid hsl(354deg, 89%, 65%);
  box-shadow: 0 0 12px rgba(245, 86, 102, 0.5);
  background: transparent;
  cursor: pointer;
}
.tasks-list .task .delete-task.no-border {
  border: none;
}
.tasks-list .task .delete-task .crossmark {
  vertical-align: middle;
  fill-rule: evenodd;
  clip-rule: evenodd;
  stroke-linejoin: round;
  stroke-miterlimit: 10;
  box-shadow: inset 0px 0px 0px hsl(354deg, 89%, 65%);
  border-radius: 50%;
  background-color: transparent;
  pointer-events: none;
}
.tasks-list .task .delete-task .crossmark * {
  fill: transparent;
  stroke: transparent;
}
.tasks-list .task .delete-task .crossmark.animated {
  animation: fill-crossmark 0.4s ease-in-out 0.4s forwards, scale 0.3s ease-in-out 0.9s both;
}
.tasks-list .task .delete-task .crossmark.animated .circle {
  fill: none;
  stroke-width: 2;
  stroke-miterlimit: 10;
  stroke: hsl(354deg, 89%, 65%);
  stroke-dasharray: 79;
  stroke-dashoffset: 79;
  animation: stroke 0.6s cubic-bezier(0.65, 0, 0.45, 1) forwards;
}
.tasks-list .task .delete-task .crossmark.animated .stick-1 {
  fill: none;
  stroke: #fff;
  stroke-width: 2px;
  stroke-dasharray: 18;
  stroke-dashoffset: 18;
  animation: stroke 0.3s cubic-bezier(0.65, 0, 0.45, 1) 0.8s forwards;
}
.tasks-list .task .delete-task .crossmark.animated .stick-2 {
  fill: none;
  stroke: #fff;
  stroke-width: 2px;
  stroke-dasharray: 18;
  stroke-dashoffset: 18;
  animation: stroke 0.3s cubic-bezier(0.65, 0, 0.45, 1) 0.8s forwards;
}
.tasks-list .task .task-name {
  width: calc(100% - 84px);
  font-size: 22px;
  font-weight: 500;
  color: white;
  border: none;
  outline: none;
  user-select: none;
  background: transparent;
  cursor: pointer;
  padding: 12px;
  border-radius: 12px;
}
@media (max-width: 400px) {
  .tasks-list .task .task-name {
    font-size: 16px;
  }
}
.tasks-list .task .task-name::selection {
  background: #f5cd51;
  color: white;
}
.tasks-list .task .task-name.isEditing {
  border: 2px solid #f7ce51;
  box-shadow: 0 10px 25px rgba(245, 205, 81, 0.4);
  background: transparent;
}
.tasks-list.showCompleted .task.active {
  display: none;
}
.tasks-list.showCompleted .task.completed {
  display: flex;
}
.tasks-list.showCompleted .task.completed .checkmark {
  box-shadow: inset 0px 0px 0px 30px #56d0f5;
  transform: none;
  pointer-events: none;
}
.tasks-list.showCompleted .task.completed .checkmark .circle {
  stroke-dashoffset: 0;
  fill: none;
  stroke-width: 2;
  stroke-miterlimit: 10;
  stroke: #56d0f5;
}
.tasks-list.showCompleted .task.completed .checkmark .check {
  stroke-dashoffset: 23;
  fill: none;
  fill-rule: nonzero;
  stroke: #fff;
  stroke-width: 2.5px;
}

.add-new-task-container {
  text-align: center;
  margin-top: 32px;
}
.add-new-task-container .plus-button {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  border: none;
  cursor: pointer;
  background-color: hsl(225deg, 14%, 17%);
  border: 2px solid rgba(0, 0, 0, 0.38);
  box-shadow: 0 8px 32px 0 hsl(225deg, 14%, 12%);
  backdrop-filter: blur(40px);
  transition: all 0.3s ease-out;
}
.add-new-task-container .plus-button:hover {
  transform: translateY(-2px);
}
.add-new-task-container .plus-button img {
  vertical-align: middle;
}

.tasks-list-settings {
  width: 320px;
  border-radius: 10px;
  background-color: hsl(225deg, 14%, 17%);
  border: 1.5px solid rgba(0, 0, 0, 0.38);
  box-shadow: 0 8px 32px 0 hsl(225deg, 14%, 12%);
  backdrop-filter: blur(40px);
  padding: 16px;
  position: absolute;
  left: 50%;
  top: 5%;
  transform: translate(-50%, -5%);
  opacity: 1;
  transition: all 0.7s ease-out;
}
@media (max-width: 400px) {
  .tasks-list-settings {
    width: 240px;
    padding: 8px;
  }
}

.tabs {
  width: 100%;
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;
}
.tabs .slider {
  position: absolute;
  left: 0;
  bottom: 0;
  height: 100%;
  width: 50%;
  background: linear-gradient(45deg, rgb(245, 205, 81) 0%, rgb(247, 206, 81) 100%);
  box-shadow: 0 10px 25px rgba(245, 205, 81, 0.4);
  border-radius: 9px;
  z-index: 0;
  transition: all 0.3s linear;
}
.tabs .tab {
  width: 50%;
  height: 100%;
  display: block;
  text-align: center;
  cursor: pointer;
  padding: 16px 0 16px 0;
  border-radius: 9px;
  font-size: 16px;
  z-index: 1;
  position: relative;
  color: #7c828d;
  transition: all 0.3s linear;
}
.tabs .tab:hover {
  color: #f7ce51;
}
.tabs .tab .title {
  font-size: 16px;
}
.tabs .tab.active .title {
  font-weight: 900;
  color: hsl(225deg, 14%, 12%);
}
.tabs .tab:nth-of-type(1).active ~ .slider {
  left: 0;
}
.tabs .tab:nth-of-type(2).active ~ .slider {
  left: 50%;
}

.overlay {
  position: fixed;
  z-index: 1000;
  width: 100%;
  height: 100%;
  top: 0;
  left: 0;
  background: hsla(225deg, 14%, 14%, 0.0025);
  transition: all 1s;
  opacity: 0;
  visibility: hidden;
}

.popup {
  position: fixed;
  top: 50%;
  left: 50%;
  width: 50%;
  height: auto;
  max-width: 630px;
  min-width: 320px;
  z-index: 2000;
  visibility: hidden;
  backface-visibility: hidden;
  transform: translateX(-50%) translateY(-50%);
  perspective: 1300px;
}
@media (max-width: 400px) {
  .popup {
    min-width: 240px;
  }
}
.popup .content {
  padding: 24px;
  padding-top: 48px;
  padding-bottom: 48px;
  border-radius: 9px;
  box-shadow: 0 10px 25px rgba(124, 130, 141, 0.2);
  transition: all 0.7s;
  transform: rotateX(-70deg);
  opacity: 0;
  transform-style: preserve-3d;
  background-color: hsl(225deg, 14%, 17%);
  backdrop-filter: blur(4.5px);
  -webkit-backdrop-filter: blur(4.5px);
  border: 1.5px solid rgba(0, 0, 0, 0.38);
  box-shadow: 0 8px 32px 0 hsl(225deg, 14%, 12%);
}
@media (max-width: 400px) {
  .popup .content {
    padding: 48px 12px;
  }
}
.popup .content .input-container {
  text-align: center;
  margin-bottom: 48px;
}
@media (max-width: 400px) {
  .popup .content .input-container {
    margin-bottom: 16px;
  }
}
.popup .content .input-container .new-task-input {
  width: 100%;
  border: 2px solid #f7ce51;
  box-shadow: 0 10px 25px rgba(245, 205, 81, 0.4);
  background: transparent;
  outline: none;
  font-size: 24px;
  padding: 16px;
  border-radius: 12px;
  color: white;
  transform: translateY(100px);
  transition: all 0.8s ease-out;
  opacity: 0.1;
}
@media (max-width: 400px) {
  .popup .content .input-container .new-task-input {
    font-size: 16px;
    padding: 8px;
  }
}
.popup .content .title-text {
  text-align: center;
  margin-bottom: 16px;
  transform: translateY(80px);
  transition: all 0.7s ease-out;
  opacity: 0.1;
  color: white;
  font-size: 32px;
}
@media (max-width: 400px) {
  .popup .content .title-text {
    font-size: 20px;
  }
}
.popup .content .btn-container {
  text-align: center;
  transform: translateY(120px);
  transition: all 0.9s ease-out;
  opacity: 0.1;
}
.popup .content .btn-container .btn {
  background: linear-gradient(45deg, rgb(245, 205, 81) 0%, rgb(247, 206, 81) 100%);
  box-shadow: 0 10px 25px rgba(245, 205, 81, 0.4);
  color: white;
  transition: all 0.9s ease;
  opacity: 0.9;
}
@media (max-width: 400px) {
  .popup .content .btn-container .btn {
    font-size: 16px;
    padding: 8px 12px;
  }
}
.popup .content .btn-container .btn:hover {
  opacity: 1;
}
.popup .content .btn-container .btn.disabled {
  background: #b9bec7;
  box-shadow: 0 8px 16px rgba(185, 190, 199, 0.0025);
  pointer-events: none;
  opacity: 0.5;
}
.popup .close-btn {
  position: absolute;
  top: 4px;
  right: 11px;
  font-size: 2em;
  color: white;
  cursor: pointer;
  transition: all 0.7s;
  opacity: 0;
  transform: rotateY(90deg);
}
.popup.show {
  visibility: visible;
}
.popup.show ~ .overlay {
  opacity: 1;
  visibility: visible;
}
.popup.show .content {
  transform: rotateX(0deg);
  opacity: 1;
}
.popup.show .content .title-text {
  transform: translateY(0px);
  opacity: 1;
}
.popup.show .content .new-task-input {
  transform: translateY(0px);
  opacity: 1;
}
.popup.show .content .btn-container {
  transform: translateY(0px);
  opacity: 1;
}
.popup.show .close-btn {
  opacity: 0.7;
  transform: rotateY(0deg);
}
.popup.show ~ .tasks-list-container {
  transform: translate(-50%, calc(-50% + 200px));
  opacity: 0;
}
.popup.show ~ .tasks-list-settings {
  transform: translate(-50%, calc(-50% - 200px));
  opacity: 0;
}

@keyframes stroke {
  100% {
    stroke-dashoffset: 0;
  }
}
@keyframes scale {
  0%, 100% {
    transform: none;
  }
  50% {
    transform: scale3d(1.1, 1.1, 1);
  }
}
@keyframes fill-checkmark {
  100% {
    box-shadow: inset 0px 0px 0px 30px #56d0f5;
  }
}
@keyframes fill-crossmark {
  100% {
    box-shadow: inset 0px 0px 0px 30px hsl(354deg, 89%, 65%);
  }
}
.jssecrets {
  font-weight: 500;
  text-decoration: none !important;
  font-family: "Urbanist";
  padding: 16px;
  background: #ffc805;
  color: #000000;
  font-size: 1.2em;
  letter-spacing: 0.2px;
  border-radius: 8px;
  box-shadow: 0px 4px 12px rgba(184, 144, 0, 0.1882352941), 0px 8px 24px rgba(184, 144, 0, 0.3764705882);
  position: absolute;
  bottom: 24px;
  right: 24px;
  transition: all 0.3s;
}

.jssecrets:hover {
  transform: translateY(-4px);
}
!

JS 

              
                // Varibles
//////////////////////////////////////////////
const plusButton = document.querySelector('.plus-button');
const popup = document.querySelector('.popup');
const addNewTaskButton = document.querySelector('.add-new-task-button');
const tasksList = document.querySelector('.tasks-list');
const newTaskInput = document.querySelector('.new-task-input');
const tabs = document.querySelectorAll('.tabs .tab');
const tasksListTitle = document.querySelector('.tasks-list-title');
const popupCloseBtn = document.querySelector('.close-btn');

//////////////////////////////////////////////
// Functions
//////////////////////////////////////////////
// Utility functions

// addClass function - adds class to an element
const addClass = (element, className) => {
  element.classList.add(className);
};

// removeClass function - removes class from an element
const removeClass = (element, className) => {
  element.classList.remove(className);
};

// I've decided to create and use them,
// as there are many occurrences of this functionality
/////////////////////////////////ß/////////////

// 1. Show popup
// reveals popup window for adding new task
const showPopup = () => {
  addClass(popup, 'show');
};

// 2. Add new task
// adds new task
// I use prepared HTML
// each "Task" component consists of three elements
// "Complete" button. I use <svg>, as I have an animation effect.
// Input field. I use <input>, and not some text element, as I need to have editing functionality
// "Delete" button. I use <svg>, as I have an animation effect.
const addNewTask = () => {
  tasksList.insertAdjacentHTML(
    'beforeend',
    `<li class="task active">

        <span class="complete-task" onclick="completeTask(event)">
        <svg
        class="checkmark"
        xmlns="http://www.w3.org/2000/svg"
        viewBox="0 0 26 26"
      >
        <circle class="circle" cx="13" cy="13" r="12.5" />
        <path class="check" d="m5 13.807 4.773 4.84L21 7.353" />
      </svg>
        </span>

        <input class="task-name" ondblclick="editTask(event)" onclick="saveTask(event)" value="${newTaskInput.value}" type="text" readonly />

        <span class="delete-task" onclick="deleteTask(event)">
        <svg
        class="crossmark"
        xmlns="http://www.w3.org/2000/svg"
        viewBox="0 0 26 26"
      >
        <circle class="circle" cx="13" cy="13" r="12.5" />
        <path class="stick-1" d="m6.69 6.69 12.62 12.62" />
        <path class="stick-2" d="M6.69 19.31 19.31 6.69" />
      </svg>
        </span>
      </li>`
  );

  // set states to default

  // clean "new task" input
  newTaskInput.value = '';
  // close popup
  removeClass(popup, 'show');
  // disable "Add" button
  addClass(addNewTaskButton, 'disabled');
};

// 3. Delete task animation
const deleteTask = (event) => {
  // animation classes
  addClass(event.currentTarget, 'no-border');
  addClass(event.currentTarget.firstElementChild, 'animated');

  // I use timer, so the animation could finish
  setTimeout(() => {
    // remove "Task" component from DOM
    event.target.parentElement.remove();
  }, 1800);
};

// 4. Complete task
const completeTask = (event) => {
  //
  // animation classes
  addClass(event.currentTarget, 'no-border');
  addClass(event.currentTarget.firstElementChild, 'animated');
  removeClass(event.currentTarget, 'empty');
  //
  // I set "unCompleteTask" function onClick
  // if user decides to move the task from "Completed" back into "Active"
  event.currentTarget.setAttribute('onclick', 'unCompleteTask(event)');

  // I use timer, so the animation could finish
  setTimeout(() => {
    addClass(event.target.parentElement, 'active');
    addClass(event.target.parentElement, 'completed');
    removeClass(event.target.firstElementChild, 'animated');
  }, 1800);
};

// 4.1. Uncomplete task
const unCompleteTask = (event) => {
  // animation classes
  removeClass(event.currentTarget, 'no-border');
  addClass(event.currentTarget, 'empty');
  //
  // I set "completeTask" function onClick
  // so user can move the task from "Active" to "Completed"
  event.currentTarget.setAttribute('onclick', 'completeTask(event)');

  // I use timer, so the animation could finish
  setTimeout(() => {
    addClass(event.target.parentElement, 'active');
    removeClass(event.target.parentElement, 'completed');
  }, 300);
};

// 5. Edit task
const editTask = (event) => {
  // I remove "readonly" attribute, so user can access the input
  event.currentTarget.removeAttribute('readonly');
  // highlighting input to indicate the active state
  addClass(event.currentTarget, 'isEditing');
};

// 6. Save task
const saveTask = (event) => {
  // I add "readonly" attribute, so user can't access the input
  event.currentTarget.setAttribute('readonly', 'readonly');
  // remove the highlighting
  removeClass(event.currentTarget, 'isEditing');
};

// 7. Set active tab
const setActiveTab = (event) => {
  // tabs indication
  removeClass(document.querySelector('.tab.active'), 'active');
  addClass(event.currentTarget, 'active');

  // toggle between "Active" and "Completed" tasks
  if (event.currentTarget.classList.contains('showCompleted')) {
    addClass(tasksList, 'showCompleted');
    tasksListTitle.innerText = 'Completed tasks';
  } else {
    removeClass(tasksList, 'showCompleted');
    tasksListTitle.innerText = 'Active tasks';
  }
};

// 8. Check if input is empty
const ifEmpty = () => {
  // if new "Task" is empty then the "Add" button is disabled
  if (!newTaskInput.value.trim().length || newTaskInput.value === '') {
    addClass(addNewTaskButton, 'disabled');
  } else {
    removeClass(addNewTaskButton, 'disabled');
  }
};

// 9. Close popup
const closePopup = () => {
  // clear the input
  newTaskInput.value = '';
  // close the popup
  removeClass(popup, 'show');
  // disable the button
  addClass(addNewTaskButton, 'disabled');
};

//////////////////////////////////////////////
// Event listeners
//////////////////////////////////////////////
plusButton.addEventListener('click', showPopup);
//
addNewTaskButton.addEventListener('click', addNewTask);
//
tabs.forEach((tab) => {
  tab.addEventListener('click', setActiveTab);
});
//
newTaskInput.addEventListener('input', ifEmpty);
//
popupCloseBtn.addEventListener('click', closePopup);
!
999px

Console