spin-wheel/scripts/util.js

An easy to use, themeable component for randomising choices and prizes.

/**
 * Format a date
 * Example: `dateFormat (new Date (), "%Y-%m-%d %H:%M:%S")`
 * will return "2012-05-18 05:37:21".
 */
export function dateFormat(date, format, utc = true) {
  utc = utc ? 'getUTC' : 'get';
  return format.replace(/%[YmdHMS]/g, i => {
    if (i === '%Y') return date[utc + 'FullYear'](); // no leading zeros required
    else if (i === '%m') i = 1 + date[utc + 'Month']();
    else if (i === '%d') i = date[utc + 'Date']();
    else if (i === '%H') i = date[utc + 'Hours']();
    else if (i === '%M') i = date[utc + 'Minutes']();
    else if (i === '%S') i = date[utc + 'Seconds']();
    else return i.slice(1); // unknown code, remove %

    // add leading zero if required
    return ('0' + i).slice(-2);
  });
}

export async function loadFonts(fontNames = []) {
  // Fail silently if browser doesn't support font loading.
  if (!('fonts' in document)) return;

  const promises = [];

  for (const i of fontNames) {
    if (typeof i === 'string') promises.push(document.fonts.load('1em ' + i));
  }

  await Promise.all(promises);
}

/**
 * Attempt to load all images (of type HTMLImageElement) in the given array.
 * The browser will download the images and decode them so they are ready to be used.
 * An error will be thrown if any image fails to load.
 * See: https://developer.mozilla.org/en-US/docs/Web/API/HTMLImageElement/decode
 */
export async function loadImages(images = []) {
  const promises = [];

  for (const img of images) {
    if (img instanceof HTMLImageElement) promises.push(img.decode());
  }

  try {
    await Promise.all(promises);
  } catch (error) {
    throw new Error('An image could not be loaded');
  }
}

/**
 * Return an array of getters and setters on the instance
 */
export function getInstanceProperties(instance) {
  return {
    getters:
      Object.entries(
        Object.getOwnPropertyDescriptors(
          Reflect.getPrototypeOf(instance)
        )
      )
      .filter(e => typeof e[1]['get'] === 'function' && e[0] !== '__proto__')
      .map(e => e[0]),

    setters:
      Object.entries(
        Object.getOwnPropertyDescriptors(
          Reflect.getPrototypeOf(instance)
        )
      )
      .filter(e => typeof e[1]['set'] === 'function' && e[0] !== '__proto__')
      .map(e => e[0]),
  };
}

/**
 * Wrapper for `setTimeout` that can be awaited.
 * Resolve after a certain duration (in milliseconds).
 */
export async function delay(duration) {
  return new Promise(resolve => setTimeout(resolve, duration));
}