CODEWITHSUNDEEP
javascriptlocal-storage
Rapture Chijioke Godson
Rapture Chijioke Godson

Reputation: 161

Clearing local storage in JavaScript

I am working on a simple todo list with vanilla JavaScript.

I have succeeded in storing the user's task in local storage and displaying the task on the frontend.

There is a clear task button to remove both tasks from local storage and on the frontend.

It works but not perfectly.

It fails when I do the following:

  1. Add a task
  2. Clear a task
  3. Add a new task and that particular task only appears on the front-end, but on local storage the previous cleared tasks and the new task appears.

If I then reload the browser, the previous task that was cleared both in the frontend and local storage appears both on frontend and local storage.

Please how do I make it work perfectly?

i.e once I clear the task in the local storage, the task does not appear again.

Here is my code below

JavaScript Code snippet

let task = document.querySelector('input'); 

const form = document.querySelector('form');

const ul = document.querySelector('ul');

const clearTask = document.querySelector('#clear');

// A list for task in local storage
const itemsLocal = localStorage.getItem("items") ? JSON.parse(localStorage.getItem("items")) : [];

localStorage.setItem("items", JSON.stringify(itemsLocal))

// convert local storage data to something I can work with in userData variable
const userData = JSON.parse(localStorage.getItem("items"));


// Function to add task
const addTask = (text) => {
// Create li element
const li = document.createElement('li');

// Create text node
li.appendChild(document.createTextNode(text));

ul.appendChild(li);
}

form.addEventListener('submit',(e) => {
    e.preventDefault();

    //  Add user task to local storage
    itemsLocal.push(task.value);  
    localStorage.setItem("items", JSON.stringify(itemsLocal))

    addTask(task.value);   
    
    // Clear input field
    task.value = '';
})


userData.forEach((data)=> {
    addTask(data);
});

clearTask.addEventListener('click', () =>{
    localStorage.removeItem("items");
    userData.length = 0;
    while (ul.firstChild) {
        ul.removeChild(ul.firstChild);
    }
    
})

HTML

<body>
    <form action="">
        <input type="text">
        <button type="submit">Add  Task</button>
    </form>
    <div>
        <ul>
            
        </ul>
    </div>
    <button id="clear">Clear Task</button>
    <script src="main.js"></script>
</body>

P.s I am new a bit new to JavaScript.

Upvotes: 1

Views: 1646

Answers (4)

StackSlave
StackSlave

Reputation: 10627

Check this out, I think you might learn from the code:

//<![CDATA[
/* js/external.js */
let get, post, doc, htm, bod, nav, M, I, mobile, S, Q, hC, aC, rC, tC, shuffle, rand, Lister; // for use on other loads
addEventListener('load', ()=>{
get = (url, success, context)=>{
  const x = new XMLHttpRequest;
  const c = context || x;
  x.open('GET', url);
  x.onload = ()=>{
    if(success)success.call(c, JSON.parse(x.responseText));
  }
  x.send();
}
post = function(url, send, success, context){
  const x = new XMLHttpRequest;
  const c = context || x;
  x.open('POST', url);
  x.onload = ()=>{
    if(success)success.call(c, JSON.parse(x.responseText));
  }
  if(typeof send === 'object' && send && !(send instanceof Array)){
    if(send instanceof FormData){
      x.send(send);
    }
    else{
      const fd = new FormData;
      for(let k in send){
        fd.append(k, JSON.stringify(send[k]));
      }
      x.send(fd);
    }
  }
  else{
    throw new Error('send argument must be an Object');
  }
  return x;
}
doc = document; htm = doc.documentElement; bod = doc.body; nav = navigator; M = tag=>doc.createElement(tag); I = id=>doc.getElementById(id);
mobile = nav.userAgent.match(/Mobi/i) ? true : false;
S = (selector, within)=>{
  var w = within || doc;
  return w.querySelector(selector);
}
Q = (selector, within)=>{
  var w = within || doc;
  return w.querySelectorAll(selector);
}
hC = function(node, className){
  return node.classList.contains(className);
}
aC = function(){
  const a = [].slice.call(arguments), n = a.shift();
  n.classList.add(...a);
  return aC;
}
rC = function(){
  const a = [].slice.call(arguments), n = a.shift();
  n.classList.remove(...a);
  return rC;
}
tC = function(){
  const a = [].slice.call(arguments), n = a.shift();
  n.classList.toggle(...a);
  return tC;
}
shuffle = array=>{
  let a = array.slice(), i = a.length, n, h;
  while(i){
    n = Math.floor(Math.random()*i--); h = a[i]; a[i] = a[n]; a[n] = h;
  }
  return a;
}
rand = (min, max)=>{
  let mn = min, mx = max;
  if(mx === undefined){
    mx = mn; mn = 0;
  }
  return mn+Math.floor(Math.random()*(mx-mn+1));
}
Lister = function(inInput, addButton, outList, clearButton, reverseButton, controlDiv = null){
  const o = localStorage.listObj ? JSON.parse(localStorage.listObj) : {lastFirst:true, list:[]}, la = o.list;
  outList.innerHTML = '';
  this.lastFirst = o.lastFirst;
  this.save = ()=>{
    localStorage.listObj = JSON.stringify(o);
    return this;
  }
  this.createItem = value=>{
    let li = M('li'), x = M('input');
    x.className = 'warn'; x.type = 'button'; x.value = 'REMOVE'; li.textContent = value; li.appendChild(x);
    x.onclick = ()=>{
      for(let i=0,c=outList.children,l=c.length; i<l; i++){
        if(c[i] === li){
          la.splice(i, 1); break;
        }
      }
      outList.removeChild(li);
      if(controlDiv && !outList.hasChildNodes())aC(controlDiv, 'hid');
      this.save();
    }
    return li;
  }
  this.addItem = value=>{
    let v = value.trim();
    if(v !== ''){
      let li = this.createItem(v), fc = outList.firstChild;
      if(this.lastFirst && fc){
        outList.insertBefore(li, fc); la.unshift(v);
      }
      else{
        outList.appendChild(li); la.push(v);
      }
      this.save();
      if(controlDiv)rC(controlDiv, 'hid');
    }
  }
  const addIt = ()=>{
    this.addItem(inInput.value); inInput.value = ''; rC(inInput, 'good');
  }
  addButton.onclick = ()=>{
    addIt();
  }
  inInput.onkeydown = e=>{
    if(e.key === 'Enter')addIt();
  }
  inInput.oninput = function(){
    const f = this.value.trim() === '' ? rC : aC;
    f(this, 'good');
  }
  clearButton.onclick = function(){
    localStorage.removeItem('listObj'); la.splice(0); outList.innerHTML = '';
    if(controlDiv)aC(controlDiv, 'hid');
  }
  this.reverse = ()=>{
    la.reverse(); outList.innerHTML = '';
    la.forEach(v=>{
      outList.appendChild(this.createItem(v));
    });
    o.lastFirst = this.lastFirst = !this.lastFirst; localStorage.listObj = JSON.stringify(o);
  }
  reverseButton.onclick = ()=>{
    this.reverse();
  }
  if(la.length){
    la.forEach(v=>{
      outList.appendChild(this.createItem(v));
    });
  }
  if(controlDiv && outList.hasChildNodes())rC(controlDiv, 'hid');
}
// magic under here
const lister = new Lister(I('input_item'), I('add_item'), I('items'), I('clear'), I('reverse'), I('control'));
}); // end load
//]]>
/* css/external.css */
*{
  box-sizing:border-box; font:22px Tahoma, Geneva, sans-serif; color:#000; padding:0; margin:0; overflow:hidden;
}
html,body,.main{
  width:100%; height:100%;
}
.main{
  background:#333; overflow-y:auto;
}
input[type=text].good{
  border:1px solid #0c0;
}
.hid{
  display:none;
}
#lister{
  padding:10px; background:#aaa;
}
input{
  height:38px; padding:3px 5px;
}
input[type=text]{
  width:calc(100% - 70px); background:#fff; border:1px solid #c00; border-radius:3px;
}
input[type=button]{
  color:#fff; font-weight:bold; border:0; border-radius:5px; cursor:pointer;
}
#add_item{
  width:70px; background:linear-gradient(#679467,#235023);
}
li{
  position:relative; height:32px; background:#ccc; padding:3px 10px; margin:5px;
}
.warn{
  background:linear-gradient(#b75757,#502323); padding:3px 15px;
}
li>.warn{
  position:absolute; right:5px; height:26px; font-size:14px;
}
#control{
  background:#bbb; text-align:center; padding:5px; border:5px solid #ccc;
}
#reverse.warn{
  background:linear-gradient(#1b7bbb,#147);
}
.warn+.warn{
  margin-left:20px;
}
<!DOCTYPE html>
<html xmlns='http://www.w3.org/1999/xhtml' xml:lang='en' lang='en'>
  <head>
    <meta charset='UTF-8' /><meta name='viewport' content='width=device-width, height=device-height, initial-scale:1, user-scalable=no' />
    <title>Title Here</title>
    <link type='text/css' rel='stylesheet' href='css/external.css' />
    <script src='js/external.js'></script>
  </head>
<body>
  <div class='main'>
    <div id='lister'>
      <input id='input_item' type='text' maxlength='239' /><input id='add_item' type='button' value='ADD' />
      <ul id='items'></ul>
      <div class='hid' id='control'><input class='warn' id='clear' type='button' value='CLEAR' /><input class='warn' id='reverse' type='button' value='REVERSE' /></div>
    </div>
  </div>
</body>
</html>

Of course, localStorage will have to be tested on your Server (maybe localhost), since it's an issue on Stack Overflow. They should add virtual localStorage and sessionStorage to this site.

Upvotes: 0

andsilver
andsilver

Reputation: 5972

elementsList.innerHTML = '' will clear all items in the list.

Below code works perfectly with localStorage and it has one more additional function that can remove individual item.

Html:

<section class="container">
    <h1>TO DO LIST</h1>
    <ul></ul>
    <div class="footer">
        <input type="text" placeholder="Title..." />
        <button class="enter">Enter</button>
    </div>
    <div>
        <button class="clear">
            Clear
        </button>
    </div>
</section>

Script:

const ul = document.querySelector("ul");
const input = document.querySelector("input");
const enterBtn = document.querySelector(".enter");
const clearBtn = document.querySelector(".clear");

const LIST_LS = "lists";
let lists = [];

function saveStorage() {
  localStorage.setItem(LIST_LS, JSON.stringify(lists));
}

function clearStorage() {
  lists = [];
  ul.innerHTML = "";
  saveStorage();
}

function loadStorage() {
  const loadStorage = localStorage.getItem(LIST_LS);

  if (!loadStorage) {
    return;
  }
  const parsedList = JSON.parse(loadStorage);
  parsedList.forEach(list => createItem(list.text));
}

function onAdd() {
  const text = input.value;

  if (!text) {
    return input.focus();
  }
  createItem(text);
  input.value = "";
  input.focus();
}

function createItem(text) {
  const id = lists.length + 1;
  const itemRow = document.createElement("li");
  itemRow.setAttribute("class", "item__row");
  itemRow.innerHTML = `${text} <i class="fas fa-trash-alt" data-id=${
    itemRow.id
  }></i>`;
  itemRow.id = id;

  const delBtn = itemRow.querySelector(".fa-trash-alt");
  delBtn.addEventListener("click", deleteItem);

  ul.appendChild(itemRow);
  lists.push({ text, id });
  saveStorage();
  return itemRow;
}

function deleteItem(event) {
  const trashBtn = event.target;
  const li = trashBtn.parentNode;
  ul.removeChild(li);
  const cleanStorage = lists.filter(toDo => toDo.id !== +li.id);
  lists = cleanStorage;
  saveStorage();
}

function init() {
  loadStorage();

  enterBtn.addEventListener("click", () => onAdd());

  input.addEventListener("keypress", event => {
    if (event.key === "Enter") {
      onAdd();
    }
  });

  clearBtn.addEventListener("click", () => clearStorage());
}

init();

https://codesandbox.io/s/damp-morning-csiny

Upvotes: 0

Abdelmonaem Shahat
Abdelmonaem Shahat

Reputation: 544

  • just make the user data array empty in the clearTask like this:
clearTask.addEventListener('click', () =>{
    localStorage.removeItem("items");
    itemsLocal = [];
    userData = [];

})

Upvotes: 1

msmolcic
msmolcic

Reputation: 6557

In your clearTask event listener you have to also clear your itemsLocal array.

clearTask.addEventListener('click', () =>{
    localStorage.removeItem("items");
    itemsLocal.length = 0; // clear it here... (you got to add this line)
    userData.length = 0;
    while (ul.firstChild) {
        ul.removeChild(ul.firstChild);
    }
});

Currently, since you're not clearing it, you're adding the new value to the array which still contains the old values and are storing it to local storage.

form.addEventListener('submit',(e) => {
    e.preventDefault();

    // 'itemsLocal' still has your old values here and you're just appending to it
    itemsLocal.push(task.value);

    // storing old items and the new one in the local storage here
    localStorage.setItem("items", JSON.stringify(itemsLocal));

    // you're rendering only the currently added item so you get the
    // fake feeling that your list is fine and that local storage has issues
    addTask(task.value);  
    
    // Clear input field
    task.value = '';
});

Upvotes: 2

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