Show the estimated time to read a content.

estimated-reading-time.js

/**
 * Show the estimated time to read a content.
 *
 * Usage
 *
 * To show the estimated time in your page you need to:
 * 1 - Include in your page a container with a class that you'll pass to the function
 * 2 - Call the function passing the text container, the timer container and set echo
 *     to true to show the estimated time.
 *
 * To get only the minutes needed to read the content you need to:
 * 1 - Call the function passing the text container.
 *
 * In case the param echo is false the function return only the minutes and nothing else.
 *
 * @param {String} contentClass         The class that contain the text to read.
 * @param {String} esitmatedTimeClass   The class that will contain the estimated time
 * @param {Boolean} echo                Show the time in the element passed with estimatedTimeClass param
 * @returns {Void|Number}               If echo is true show the estimated time, otherwise it will return the minutes.
 *
 * @author Manuel Ricci
 */
function estimatedReadingTime(contentClass, esitmatedTimeClass = null, echo = false) {
  if (echo === true && esitmatedTimeClass === null) {
    console.error("If you want to show the estimated time you need to specify the param estimatedTimeClass");
    return;
  }
  const wordPerMinute = 200; // Global average.
  let content = document.querySelector(contentClass).innerText;
  let result;

  content = content.split(" ");

  if (content.length > 0) {
    let time = Math.ceil(content.length / wordPerMinute);
    if (echo) {
      result = `~ ${time} minuti di lettura`;
    } else {
      result = time;
    }
  }

  if (echo) {
    document.querySelector(esitmatedTimeClass).innerHTML += result;
  } else {
    return result;
  }
}