JSFiddle - React, Tailwind, and code Playground

by Josh Pullen

HTML

<!--
  Create timer that keeps you on track to do n questions in m minutes
  (default 23 questions in 35 minutes)
-->

CSS

h1 {
  text-align: center;
}

label {
  display: block;
  margin-bottom: 8px;
}

input[type="number"] {
  font-size: 24px;
  padding: 4px 8px;
  
}

JavaScript

import { html, render, useState, useReducer, useEffect, useCallback } from "https://unpkg.com/htm/preact/standalone.module.js";

function App() {
	const [settings, setSettings] = useState(null);

	const { time, status, start, pause, reset } = useStopwatch();
  
  if (settings === null) {
  	const onSubmit = (event) => {
    	event.preventDefault();
      
      const data = new FormData(event.target);
      reset();
      setSettings({
      	totalTime: 60 * Number(data.get("totalTime")),
        questions: Number(data.get("questions"))
      });
    }
  
    return html`
    	<h1>LSAT Timer</h1>
      <form onSubmit=${onSubmit}>
        <label>
          <div>Number of questions:</div>
          <input type="number" name="questions" defaultValue=${23} />
        </label>
        <label>
          <div>Total time (minutes):</div>
          <input type="number" name="totalTime" defaultValue=${35} />
        </label>
        <div>
          <input type="submit" value="Confirm" />
        </div>
      </form>
    `;
  }
  
	const durationPerQuestion = settings.totalTime / settings.questions;
  
  const currentQuestion = 1 + Math.floor(time / durationPerQuestion);
	const timeSpentOnQuestion = (time % durationPerQuestion) / durationPerQuestion;

	return html`
    <h1>Question ${currentQuestion}</h1>
    <div
    	style=${{
      	position: "fixed",
        top: 0,
        left: 0,
        background: "#eee",
        width: `${timeSpentOnQuestion * 100}%`,
        height: "100%",
        zIndex: -1
      }}
    />
    <div>
      ${status === "on" ? html`
        <button onClick=${pause}>Pause</button>
      ` : html`
        <button onClick=${start}>Start</button>
      `}
    </div>
    
    <div style=${{ display: "flex", position: "fixed", bottom: 4, left: 4, right: 4, gap: 4 }}>
      <button onClick=${() => setSettings(null)} style=${{ flex: "1 1 0" }}>Reset</button>
    </div>
  `;
}

function getTime(state) {
	switch (state.status) {
    case "off":
    	return...