Reading time / Words per minute

readingTime.js

/**
 * Get reading time
 * @param  {String} text  The text string to analyze
 * @return {Int}          Reading time in milliseconds
 */
function getReadingTime(text) {
  var totalWords,
    wordsPerMillisecond,
    totalReadingTime,
    wordsPerMinute = 250,
    wordsPerMillisecond = wordsPerMinute / 60000;

  text = text.replace(/<\/?[^>]+(>|$)/g, ''); // Remove any HTML-tags
  totalWords = text.split(/\s+/g).length; // Split up in words
  totalReadingTime = Math.floor(totalWords / wordsPerMillisecond);

  return totalReadingTime;
}

/**
# Average word per minute

Third-grade students = 150
Eight grade students = 250
Average adult: 300
Average college student = 450
Average “high level exec” = 575
Average college professor = 675
Speed readers = 1,500
World speed reading champion = 4,700
*/

You can do fun stuff like this:

var readingTime = getReadingTime(document.body.textContent);

navigator.getBattery().then(function(battery) {
  if ((readingTime * 1000) > battery.dischargingTime) {
    alert('You won’t be able to finish this article. Charge your battery!');
  }
});