ToDo App with Preact


Follow the Setting up Preact tutorial to set up the proper base for this ToDo application.

Custom CSS

You can use a custom CSS for a nicer visual effect. Add the following CSS link to the <head> section in config/client/index.html:

<link rel="stylesheet" href="">

Create App Component

In features/Base/View/index.tsx replace the content with the following code:

import { h } from 'preact';
import { useState, useEffect } from 'preact/hooks';

interface Task {
  name: string;
  done: boolean

function App() {
  const [newTask, setNewTask] = useState('');
  const [tasks, setTasks] = useState([] as Task[]);

  const addTodo = () => {
    setTasks([...tasks, { name: newTask, done: false }]);

  const onInput = (event: Event) => {
    const { value } = as HTMLInputElement;

  const onKeyUp = (event: KeyboardEvent) => {
    const { key } = event;
    if (key === 'Enter') {

  return (
    <div class="task-container">
      <div class="task-input">
          placeholder="Add new item..."
        <button class="task-add" onClick={addTodo}>Add</button>
      <ul class="task-list">
        {, index) => (
          <li key={index} class="task-item" v-for="task in state.tasks">
            <label class="task-item-container">
              <div class="task-checkbox">
                <input type="checkbox" class="opacity-0 absolute" value={task.done} />
                <svg class="task-checkbox-icon" viewBox="0 0 20 20">
                  <path d="M0 11l2-2 5 5L18 3l2 2L7 18z" />
              <div class="ml-2">{}</div>

export { App };

REST Endpoint

In features/Task/Controller create browse.ts. The naming is important. The browse name corresponds to the HTTP GET request that is supposed to respond with a collection of a given resource. In this case, it's a collection of tasks.

We create a handler function that describes the action that will happen once such request is received. In Kretes, handlers are functions that take HTTP requests as input and return HTTP responses as output. The OK convenience wrapper corresponds to the 200 OK response. We define the list of tasks in memory for now, as the tasks variable.

import { Handler, response } from 'kretes';

const { OK } = response;

const tasks = [
  { name: 'Use TypeScript 4.x', done: false },
  { name: 'Learn Kretes', done: false },
  { name: 'Enjoy programming', done: false },

export const browse: Handler = ({ params }) => {
  return OK(tasks);

Data Fetching

Connect the front-end with the REST endpoint using the useEffect hook and the built-in fetch browser API.

const fetchData = async () => {
  const response = await fetch('/task');
  const result = await response.json();

useEffect(() => fetchData(), [])


Preact ToDo with Kretes

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