Simple Todo server application.

index.js

const express = require('express')
const app = express()

let todos = []

app.get('/', function(req, res) {
    const todosHtml = todos.map(function(todo, idx) {
        let status = ''
        if (todo.done == true) {
            status = 'checked'
        }
        return `
        <div>
            <input type="checkbox" ${status} onclick="window.location.href='./completeTask?index=${idx}'">
            ${todo.task}
        </div>`
    })
    res.send(`
        <h1>Todo List</h1>
        <form action="/add">
            <input name="newTaskFromUser">
            <button>Submit</button>
        </form>
        <p>${todosHtml.join('')}</p>
    `)
})

app.get('/add', function(req, res) {
    const newTask = req.query.newTaskFromUser
    const newTodo = {
        task: newTask,
        done: false
    }
    todos.push(newTodo)
    res.redirect('/')
})

app.get('/completeTask', function(req, res) {
    const todoIndex = req.query.index
    todos[todoIndex].done = !todos[todoIndex].done
    res.redirect('/')
})

app.listen(3000, function() {
    console.log('Server is running ...')
})