// Credit David Walsh (https://davidwalsh.name/javascript-debounce-function)

// Returns a function, that, as long as it continues to be invoked, will not
// be triggered. The function will be called after it stops being called for
// N milliseconds. If `immediate` is passed, trigger the function on the
// leading edge, instead of the trailing.
function debounce(func, wait, immediate) {
  var timeout;

  // This is the function that is actually executed when
  // the DOM event is triggered.
  return function executedFunction() {
    // Store the context of this and any
    // parameters passed to executedFunction
    var context = this;
    var args = arguments;
      
    // The function to be called after 
    // the debounce time has elapsed
    var later = function() {
      // null timeout to indicate the debounce ended
      timeout = null;
      
      // Call function now if you did not on the leading end
      if (!immediate) func.apply(context, args);
    };

    // Determine if you should call the function
    // on the leading or trail end
    var callNow = immediate && !timeout;
  
    // This will reset the waiting every function execution.
    // This is the step that prevents the function from
    // being executed because it will never reach the 
    // inside of the previous setTimeout  
    clearTimeout(timeout);
  
    // Restart the debounce waiting period.
    // setTimeout returns a truthy value (it differs in web vs node)
    timeout = setTimeout(later, wait);
  
    // Call immediately if you're dong a leading
    // end execution
    if (callNow) func.apply(context, args);
  };