Here is my interpretation of how to create a simple JavaScript ToDo list based on immutability and states. You may also enjoy the JavaScript for beginners - learn by doing course.
So far there are only add and delete actions created:
<input id="myInput" type="text" /><button id="Add">Add new Todo </button>
<div id="app"></div>
<script>
// state object
var state = {
name: 'todo list 1',
todos: [{ id: 1, data: 'first todo <button class="delete" data-id="1">X</button>' }]
};
//we pass the todo as object({with id, and the todo_info})
function applyAction(todo, action) {
switch (action) {
case 'add':
return [...state.todos, todo];
break
case 'remove':
//here remove it from index using todo.id
return state.todos
.filter(dbTodo => dbTodo.id !== todo.id);
break
case 'update':
// return [
// ...state.todos
// .filter(dbTodo => dbTodo.id !== todo.id), // first we remove the soon to be updated todo
// todo // then we add the updated version to the end of the array
// ];
return state.todos.map(
dbTodo =>
// whe check when we have match on id, we use todo, otherwise we leave the original dbTodo
dbTodo.id === todo.id ? todo : dbTodo
);
break
}
}
let renderTodos = todos => {
return `
<ul>${state.todos.map(todo => `
<li>${todo.data}</li>
`)} `;
}
// The state-based UI rendering
var render = state => {
var html = `
<h1>
${state.name}</h1>
${ state.todos.length < 1 ? 'Please add a todo' : ''} ${renderTodos(state.todos)} `; app.innerHTML = html; }; let setState = obj => {
// update the state with passed object
Object.keys(obj).forEach(key => {
state[key] = obj[key];
});
//update the render
render(state);
}
// Add todo event listener
document.querySelector('#Add').addEventListener('click', () => {
// get what's inside the input
const inputData = document.querySelector('#myInput');
if (inputData.value == '') return;
// just mapping into new array only the ids, then doing max on them
let lastId = (state.todos.length > 0) ? Math.max(...state.todos.map(todo => todo.id)) : 0;
current_todo = { id: ++lastId, data: `${inputData.value} <button class="delete" data-id="${lastId}">X</button>` }
setState({ //save the modified state and show the result
todos: applyAction(current_todo, 'add') // apply the add modification to the state
});
// clear the value inside the input
inputData.value = '';
});
// Remove todo event listener
document.querySelector('#app').addEventListener('click', (e) => {
if (e.target.classList.contains('delete')) {
const id = +e.target.getAttribute('data-id'); // convert the string data-id to number
const currentTodo = { id };
setState({ // save the modified state and show the result
todos: applyAction(currentTodo, 'remove') // apply the add modification to the state
});
}
});
// Render the initial UI
var app = document.querySelector('#app'); render(state);
</script>
Congratulations !
Resources:
JavaScript for beginners - learn by doing