Develop Reference

Problem with sessionStorage: I am not displaying the first item correctly

I am having a problem with sessionStorage; in particular, I want the id of the ads to be saved in the session where the user puts the like on that particular favorite article.
However, I note that the array of objects that is returned contains the ids starting with single quotes, as shown below:
['', '1', '7']
but I want '1' to be shown to me directly.
While if I go into the sessionStorage I notice that like is shown as:
,1,7
ie with the leading comma, but I want it to start with the number directly.
How can I fix this?
function likeAnnunci(){
let likeBtn = document.querySelectorAll('.like');
likeBtn.forEach(btn => {
btn.addEventListener('click', function(){
let id = btn.getAttribute('ann-id');
//sessionStorage.setItem('like', [])
let storage = sessionStorage.getItem('like').split(',');
//console.log(storage);
if(storage.includes(id)){
storage = storage.filter(id_a => id_a != id);
} else {
storage.push(id);
}
sessionStorage.setItem('like', storage)
console.log(sessionStorage.getItem('like').split(','));
btn.classList.toggle('fas');
btn.classList.toggle('far');
btn.classList.toggle('tx-main');
})
})
};
function setLike(id){
if(sessionStorage.getItem('like')){
let storage = sessionStorage.getItem('like').split(',');
if(storage.includes(id.toString())){
return `fas`
} else {
return `far`
}
} else {
sessionStorage.setItem('like', '');
return`far`;
}
}

The main issue you're having is that you're splitting on a , instead of using JSON.parse().
Also, you've got some other code issues and logical errors.
Solution:
function likeAnnunci() {
const likeBtn = document.querySelectorAll('.like');
likeBtn.forEach((btn) => {
btn.addEventListener('click', function () {
let id = btn.getAttribute('ann-id');
//sessionStorage.setItem('like', [])
let storage = JSON.parse(sessionStorage.getItem('like') || '[]');
//console.log(storage);
if (!storage.includes(id)) {
storage.push(id);
}
sessionStorage.setItem('like', JSON.stringify(storage));
console.log(JSON.parse(sessionStorage.getItem('like')));
btn.classList.toggle('fas');
btn.classList.toggle('far');
btn.classList.toggle('tx-main');
});
});
}
More modular and optimal solution:
const likeBtns = document.querySelectorAll('.like');
// If there is no previous array stored, initialize it as an empty array
const initLikesStore = () => {
if (!sessionStorage.getItem('likes')) sessionStorage.setItem('likes', JSON.stringify([]));
};
// Get the item from sessionStorage and parse it into an array
const grabLikesStore = () => JSON.parse(sessionStorage.getItem('likes'));
// Set a new value for the likesStore, automatically serializing the value into a string
const setLikesStore = (array) => sessionStorage.setItem('likes', JSON.stringify(array));
// Pass in a value.
const addToLikesStore = (value) => {
// Grab the current likes state
const pulled = grabStorage();
// If the value is already there, do nothing
if (pulled.includes(value)) return;
// Otherwise, add the value and set the new array
// of the likesStore
storage.push(value);
setLikesStore(pulled);
};
const likeAnnunci = (e) => {
// Grab the ID from the button clicked
const id = e.target.getAttribute('ann-id');
// Pass the ID to be handled by the logic in the
// function above.
addToLikesStore(id);
console.log(grabLikesStore());
btn.classList.toggle('fas');
btn.classList.toggle('far');
btn.classList.toggle('tx-main');
};
// When the dom content loads, initialize the likesStore and
// add all the button event listeners
window.addEventListener('DOMContentLoaded', () => {
initLikesStore();
likeBtns.forEach((btn) => btn.addEventListener('click', likeAnnunci));
});

Delete a record in indexdb from a button in a dynamically created row

I have a table with rows which gets added dynamically to the DOM from a row inside template tags. In the row I have a delete button which deletes the row from the table and should also delete the entry from the IndexDB. The method to delete the entry gets called from the onclick event listener of the delete button. The request.onsuccess from the IndexDB triggers but the database entry is not disappearing.
The same method called from the console to delete the entry with the same key is successful. Same if I call the method from a button which is not added to the DOM afterwards. So I assume the problem lays in this method which creates the table rows from a template.
UPDATED: Changed the method to not work on the document fragment table data cells from the template but on a clone (https://developer.mozilla.org/en-US/docs/Web/HTML/Element/template#Avoiding_DocumentFragment_pitfall). Attaching now the event handler after appending to the table doesn't change anythinh. The handler gets attached and by click on the button the code inside gets called but still the entry is not deleted from the IndexDB.
/**
* Create the visual element of the task object and its properties and append it to the
* task table
*
* #param {*} task the task data object
*/
function addTaskToTaskList(task) {
let taskTableBody = document.querySelector('#task-table tbody');
// get the task template
let template = document.querySelector("#task-item-template");
// clone the new row and insert it into the table
let clone = template.content.firstElementChild.cloneNode(true);
let tableCells = clone.querySelectorAll('td');
// fill the cells with the data from the task object
tableCells[0].innerHTML = task.tID;
tableCells[1].innerHTML = task.title;
tableCells[2].innerHTML = task.startDate;
tableCells[3].innerHTML = task.endDate;
tableCells[4].innerHTML = task.priority;
// add the task node to the table
let appendedNode = taskTableBody.appendChild(clone);
// add eventlisteners for action buttons
let actionBtns = appendedNode.querySelectorAll('button');
actionBtns[1].addEventListener('click', function (event) {
let rowClicked = this.parentNode.parentNode;
let taskID = rowClicked.querySelector('#task-id').innerHTML;
console.log("TaskID extracted from row: " + taskID);
Database.deleteItemInObjectStore("Tasks", taskID);
removeTaskFromTable(rowClicked.rowIndex);
});
}
The method call Database.deleteItemInObjectStore("Tasks", taskID); is correct and triggers the request.onsucces from the IndexDB objectstore, also from the button in the row I created. But the entry is not deleted from the IndexDB.
Sample rendered table:
function deleteItemInObjectStore(objectStoreName, itemKey) {
let request = window.indexedDB.open(dbName, dbVersion)
request.onsuccess = function (e) {
let db = e.target.result;
let tx = db.transaction(objectStoreName, "readwrite");
let store = tx.objectStore(objectStoreName);
let req = store.delete(itemKey);
req.onsuccess = function () {
console.log("DATABASE | Successful deleted from Objectstore: "+
objectStoreName + " | The item with key: " + itemKey);
}
tx.oncomplete = function () {
db.close();
}
}
}
Sample console output. For example I click in the first row on delete:
TaskID extracted from row: 1
DATABASE | Successful deleted from Objectstore: Tasks | The item with key: 1
Same method called from the console with the same arguments with exactly the same output works without problems:
Database.deleteItemInObjectStore("Tasks", 1);
DATABASE | Successful deleted from Objectstore: Tasks | The item with key: 1

The solution: I get task id from the row as string but to delete the indexDB entry with the key i need to parse it as a number.
function deleteItemInObjectStore(objectStoreName, itemKey) {
let request = window.indexedDB.open(dbName, dbVersion)
request.onsuccess = function (e) {
let db = e.target.result;
let tx = db.transaction(objectStoreName, "readwrite");
let store = tx.objectStore(objectStoreName);
let req = store.delete(Number(itemKey));
req.onsuccess = function () {
console.log("DATABASE | Successful deleted from Objectstore: "+
objectStoreName + " | The item with key: " + itemKey);
}
tx.oncomplete = function () {
db.close();
}
}
}

How would I use local storage for a to do list?

I am being asked to have a to do list and save each task (that the user supplies as well as original) through local storage. My teacher did a very simple demo on something completely different and I spent a few hours trying to figure it out. When I looked at the solution, I honestly cannot figure it out. It looks really complicated, and I don't even know where to start. If anyone can give me any hints, that would be awesome!
My code:
let ul = document.querySelector('ul');
let newItem = document.querySelector('input[type=text]');
let checkbox = document.createElement('input');
checkbox.setAttribute('type', 'checkbox');
function output() {
let newTodo = document.createElement('li');
newTodo.innerText = newItem.value;
newTodo.classList.add('todo');
let ulAppend = ul.append(newTodo);
ul.append(newTodo);
let checkboxAppend = newTodo.append(checkbox);
newTodo.append(checkbox);
newItem.value = '';
}
let button = document.querySelector('.btn');
button.addEventListener('click', output);
ul.addEventListener('click', function(e) {
if (e.target.tagName === 'LI') {
e.target.remove();
} else if (e.target.tagName === 'INPUT') {
e.target.parentElement.classList.toggle('finished');
}
});
My teacher's code/local storage solution:
const todoForm = document.getElementById("newTodoForm");
const todoList = document.getElementById("todoList");
// retrieve from localStorage
const savedTodos = JSON.parse(localStorage.getItem("todos")) || [];
for (let i = 0; i < savedTodos.length; i++) {
let newTodo = document.createElement("li");
newTodo.innerText = savedTodos[i].task;
newTodo.isCompleted = savedTodos[i].isCompleted ? true : false;
if (newTodo.isCompleted) {
newTodo.style.textDecoration = "line-through";
}
todoList.appendChild(newTodo);
}
todoForm.addEventListener("submit", function(event) {
event.preventDefault();
let newTodo = document.createElement("li");
let taskValue = document.getElementById("task").value;
newTodo.innerText = taskValue;
newTodo.isCompleted = false;
todoForm.reset();
todoList.appendChild(newTodo);
// save to localStorage
savedTodos.push({ task: newTodo.innerText, isCompleted: false });
localStorage.setItem("todos", JSON.stringify(savedTodos));
});
todoList.addEventListener("click", function(event) {
let clickedListItem = event.target;
if (!clickedListItem.isCompleted) {
clickedListItem.style.textDecoration = "line-through";
clickedListItem.isCompleted = true;
} else {
clickedListItem.style.textDecoration = "none";
clickedListItem.isCompleted = false;
}
// breaks for duplicates - another option is to have dynamic IDs
for (let i = 0; i < savedTodos.length; i++) {
if (savedTodos[i].task === clickedListItem.innerText) {
savedTodos[i].isCompleted = clickedListItem.isCompleted;
localStorage.setItem("todos", JSON.stringify(savedTodos));
}
}
});
Even though my code is more simpler (at least from what I can tell), it works exactly as his code does.

Local storage saves a JSON object to the user's computer. You should create an array of todos, append that array with every new todo, then set that item to local storage.
let ul = document.querySelector('ul');
const savedTodos = JSON.parse(localStorage.getItem("todos")) || []; // Retrieves local storage todo OR creates empty array if none exist
let newItem = document.querySelector('input[type=text]');
let checkbox = document.createElement('input');
checkbox.setAttribute('type', 'checkbox');
function output() {
let newTodo = document.createElement('li');
newTodo.innerText = newItem.value;
newTodo.classList.add('todo');
ul.append(newTodo);
newTodo.append(checkbox);
savedTodos.push({task: newItem.value, isCompleted: false}); // Appends the new todo to array
localStorage.setItem("todos", JSON.stringify(savedTodos)); //Converts object to string and stores in local storage
newItem.value = '';
}

I've annotated the solution you posted with some comments to help you step through it.
// Retrieve elements and store them in variables
const todoForm = document.getElementById("newTodoForm");
const todoList = document.getElementById("todoList");
// Get data stored in localStorage under the key "todos".
// The data type will be a string (local storage can only store strings).
// JSON is a global object that contains methods for working with data represented as strings.
// The `||` syntax is an OR operator and is used here to set an empty array as a fallback in case `localStorage` is empty
const savedTodos = JSON.parse(localStorage.getItem("todos")) || [];
// Create a loop the same length as the list of todos
for (let i = 0; i < savedTodos.length; i++) {
// Create an <li> element in memory (does not appear in the document yet)
let newTodo = document.createElement("li");
// Set the inner text of that new li with the contents from local storage.
// The savedTodos[i] is accessing data in the localStorage array.
// The [i] is a different number each loop.
// The `.task` is accessing 'task' property on the object in the array.
newTodo.innerText = savedTodos[i].task;
// Create a new property on the element called `isCompleted` and assign a boolean value.
// This is only accessible in code and will not show up when appending to the DOM.
newTodo.isCompleted = savedTodos[i].isCompleted ? true : false;
// Check the value we just set.
if (newTodo.isCompleted) {
// Create a style for the element if it is done (strike it out)
newTodo.style.textDecoration = "line-through";
}
// Actually append the new element to the document (this will make it visible)
todoList.appendChild(newTodo);
}
// `addEventListener` is a function that registers some actions to take when an event occurs.
// The following tells the browser - whenever a form is submitted, run this function.
todoForm.addEventListener("submit", function(event) {
// Don't try to send the form data to a server. Stops page reloading.
event.preventDefault();
// Create a <li> element in memory (not yet visible in the document)
let newTodo = document.createElement("li");
// Find element in the document (probably a input element?) and access the text value.
let taskValue = document.getElementById("task").value;
// Set the text of the <li>
newTodo.innerText = taskValue;
// Set a property on the <li> call `isCompleted`
newTodo.isCompleted = false;
// Empty out all the input fields in the form
todoForm.reset();
// Make the new <li> visible in the document by attaching it to the list
todoList.appendChild(newTodo);
// `push` adds a new element to the `savedTodos` array. In this case, an object with 2 properties.
savedTodos.push({ task: newTodo.innerText, isCompleted: false });
// Overwrite the `todos` key in local storage with the updated array.
// Use the JSON global object to turn an array into a string version of the data
// eg [1,2,3] becomes "[1,2,3]"
localStorage.setItem("todos", JSON.stringify(savedTodos));
});
// This tells the browser - whenever the todoList is clicked, run this function.
// The browser will call the your function with an object that has data about the event.
todoList.addEventListener("click", function(event) {
// the `target` of the event is the element that was clicked.
let clickedListItem = event.target;
// If that element has a property called `isCompleted` set to true
if (!clickedListItem.isCompleted) {
// update the styles and toggle the `isCompleted` property.
clickedListItem.style.textDecoration = "line-through";
clickedListItem.isCompleted = true;
} else {
clickedListItem.style.textDecoration = "none";
clickedListItem.isCompleted = false;
}
// The code above changes the documents version of the data (the elements themselves)
// This loop ensures that the array of todos data is kept in sync with the document
// Loop over the array
for (let i = 0; i < savedTodos.length; i++) {
// if the item in the array has the same text as the item just clicked...
if (savedTodos[i].task === clickedListItem.innerText) {
// toggle the completed state
savedTodos[i].isCompleted = clickedListItem.isCompleted;
// Update the localStorage with the new todos array.
localStorage.setItem("todos", JSON.stringify(savedTodos));
}
}
});
Keep in mind, there are 2 sources of state in your todo list. One is how the document looks, and the other is the array of todos data. Lots of challenges come from making sure these 2 stay in sync.
If somehow the document showed one of the list items as crossed out, but your array of data shows that all the todos are not completed, which version is correct? There is no right answer here, but state management will be something you might consider when designing apps in the future. Redux is a good js library with a well understood pattern that helps solve this problem. Hope this last comment doesn't confuse too much. Best of luck!

The important part is in (de)serializing the data. That means:
reading from localStorage (JSON.parse(localStorage.getItem("todos")) || [])
We add the default [] because if the todos key does not exist, we will get null and we expect a list
saving to localStorage (localStorage.setItem("todos", JSON.stringify(savedTodos)))
We need JSON.parse and its complementary operation JSON.stringify to parse and save strings because localStorage can store only strings.
In your case you need to read the data from localStorage and render the initial list. To save it to localStorage, again, you have to serialize the data. See the below snippets (link to working JSFIDDLE, because the below example does not work in the StackOverflow sandbox environment):
let ul = document.querySelector('ul');
let newItem = document.querySelector('input[type=text]');
const Store = {
serialize () {
return [].slice.call(document.querySelectorAll("li")).map(c => {
return {
text: c.textContent,
finished: c.querySelector("input").checked
}
})
},
get () {
return JSON.parse(localStorage.getItem("todos")) || []
},
save () {
return localStorage.setItem("todos", JSON.stringify(Store.serialize()))
}
}
const firstItems = Store.get()
firstItems.forEach(it => {
output(it.text, it.finished)
})
function output(v, finished) {
let newTodo = document.createElement('li');
newTodo.innerText = v || newItem.value;
newTodo.classList.add('todo');
let ulAppend = ul.append(newTodo);
ul.append(newTodo);
// Create a checkbox for each item
let checkbox = document.createElement('input');
if (finished) {
checkbox.checked = true
}
checkbox.setAttribute('type', 'checkbox');
let checkboxAppend = newTodo.append(checkbox);
newTodo.append(checkbox);
newItem.value = '';
}
let button = document.querySelector('.btn');
button.addEventListener('click', () => {
output()
Store.save()
});
ul.addEventListener('click', function(e) {
if (e.target.tagName === 'LI') {
e.target.remove();
} else if (e.target.tagName === 'INPUT') {
e.target.parentElement.classList.toggle('finished');
}
// Update the value in localStorage when you delete or add a new item
Store.save()
});
<ul></ul>
<input type="text" /> <button class="btn">Submit</button>
I have added the Store variable to simplify the way you get and set the data in localStorage.
The serialize method will read the TODOs from the list. document.querySelectorAll("li") returns a NodeList, but by doing [].slice.call(...) we convert it to an Array.

Save multiple objects in a sessionStorage

I am trying to save objects in a sessionStorage anytime I click on a bookmark icon. But instead of saving several objects. Anytime I click on my icon bookmark to save a book; it is being overridden by the new value.
How could I add several objects (books) in my sessionStorage?
Thanks
here is the code snippet
try {
const responseData = await sendHttpRequest(
'GET',
"https://www.googleapis.com/books/v1/volumes?q=" + search );
const listOfBooks = responseData;
console.log(listOfBooks);
for (i=0; i < listOfBooks.items.length; i++) {
console.log(listOfBooks.items[i]);
const postEl = document.importNode(template.content, true);
console.log("postEl", postEl);
//BookMark Icon event
const target = postEl.querySelector('.icon-bookmark');
target.addEventListener('click', () => {
sessionStorage.setItem('bookStorage', bookStorage);
sessionStorage.setItem('bookStorage' , JSON.stringify(bookStorage));
const extractedBook = sessionStorage.getItem('bookStorage');
const extractedBookInfo = JSON.parse(sessionStorage.getItem('bookStorage'));
console.log(extractedBookInfo);
});
postEl.querySelector('.id').textContent = 'id: '+ listOfBooks.items[i].id;
postEl.querySelector('.titre').textContent = 'Titre: '+ listOfBooks.items[i].volumeInfo.title;
postEl.querySelector('.author').textContent = 'Auteur: '+ listOfBooks.items[i].volumeInfo.authors;
postEl.querySelector('.desc').textContent ='Description: '+ listOfBooks.items[i].volumeInfo.description;
postEl.querySelector('img').src = listOfBooks.items[i].volumeInfo.imageLinks.thumbnail;
if (postEl.querySelector('.desc').textContent.length > 200) {
postEl.querySelector('.desc').textContent = postEl.querySelector('.desc').textContent.substring(0,200);
}
if (!postEl.querySelector('img').src) {
postEl.querySelector('img').src ="resources/css/img/unavailable.png";
}
listElement.append(postEl);
const bookStorage = {
id: listOfBooks.items[i].id,
title: listOfBooks.items[i].volumeInfo.title,
author: listOfBooks.items[i].volumeInfo.authors,
desc: listOfBooks.items[i].volumeInfo.description,
img: listOfBooks.items[i].volumeInfo.imageLinks.thumbnail
};
}
} catch (error) {
alert(error.message);
}
}
btnRechercher.addEventListener('click', fetchBooks, false);

You can only have unique keys inside session storage, that’s why everytime you insert a new entity with the same key the storage overwrites the old one. You can do a for and save every book, for example ‘book_1’, ‘book_2’. Or you can store an array, but you have to use json.stringify(name_of_your_array) and then when you want your array back you can use json.parse(storage.getItem(key))

retrieve local storage at regular intervals

In order to append <form> inputs to localStorage, I'm using this piece of code:
function appendToStorage(name, data){
var old = localStorage.getItem(name);
if(old === null) old = '';
localStorage.setItem(name, old + data);
}
userInputs();
function userInputs() {
appendToStorage('oldData', $('textarea[name="textbox"]').val());
}
but I want to retrieve localStorage and process its individual words, split byspaces, every minute or so.
Does this...
function setInput(){
var input = userInputs();
setInterval(function(){localStorage.getItem(name)}, 60000);
}
...make any sense?