JavaScript Programming/Date and Time/Example Code

example.html edit

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="Cache-Control" content="no-cache">
  <title>Example</title>
  <style>
    body {
      font-family: Arial, Helvetica, sans-serif;
    }
  </style>
  <script defer src="example.js"></script>
</head>

<body>
  <noscript>Enable JavaScript to see web page content.</noscript>

  <h1>Date and Time</h1>

  <p>
    <label for="date">Select a date:</label>
    <input type="date" id="date"></input>
  </p>

  <p>
    <label for="iso">ISO:</label>
    <output id="iso"></output><br>

    <label for="utc">UTC:</label>
    <output id="utc"></output>
  </p>

  <p>
    <label for="now">Now:</label>
    <output id="now"></output>
  </p>

  <p>
    <label for="code1">Code 1:</label>
    <output id="code1"></output>
    <button id="code1-button">Run</button><br>

    <label for="code2">Code 2:</label>
    <output id="code2"></output>
    <button id="code2-button">Run</button><br>
  </p>
</body>

</html>

example.js edit

// This program displays date and time methods.
//
// References:
//   https://en.wikibooks.org/wiki/JavaScript

"use strict";

window.addEventListener("load", function () {
  document.getElementById("date").addEventListener("change", inputChange);

  window.setInterval(timerInterval, 1000);

  document.getElementById("code1-button").addEventListener("click", code1Click);
  document.getElementById("code2-button").addEventListener("click", code2Click);
});

function inputChange() {
  let value = document.getElementById("date").value;
  let date = new Date(value);

  let iso = date.toISOString();
  document.getElementById("iso").innerText = iso;

  let utc = date.toUTCString();
  document.getElementById("utc").innerText = utc;
}

function timerInterval() {
  let now = Date.now();
  document.getElementById("now").innerText = now + 
    " (milliseconds since January 1, 1970)";
}

function code1Click() {
  let start = Date.now();

  let result = "";
  // loop one million times
  for (let i = 0; i < 1000; i++) {
    for (let j = 0; j < 1000; j++) {
      result = i * j;
    }
  }
  document.getElementById("code1").innerText = result;

  let elapsed = Date.now() - start;
  document.getElementById("code1").innerText = elapsed;
}

function code2Click() {
  let start = Date.now();

  // loop one million times
  for (let i = 0; i < 1000; i++) {
    for (let j = 0; j < 1000; j++) {
      document.getElementById("code2").innerText = i * j;
    }
  }

  let elapsed = Date.now() - start;
  document.getElementById("code2").innerText = elapsed;
}