Chris@0: /**
Chris@0:  * @file
Chris@0:  * Adapted from underscore.js with the addition Drupal namespace.
Chris@0:  */
Chris@0: 
Chris@0: /**
Chris@0:  * Limits the invocations of a function in a given time frame.
Chris@0:  *
Chris@0:  * The debounce function wrapper should be used sparingly. One clear use case
Chris@0:  * is limiting the invocation of a callback attached to the window resize event.
Chris@0:  *
Chris@0:  * Before using the debounce function wrapper, consider first whether the
Chris@0:  * callback could be attached to an event that fires less frequently or if the
Chris@0:  * function can be written in such a way that it is only invoked under specific
Chris@0:  * conditions.
Chris@0:  *
Chris@0:  * @param {function} func
Chris@0:  *   The function to be invoked.
Chris@0:  * @param {number} wait
Chris@0:  *   The time period within which the callback function should only be
Chris@0:  *   invoked once. For example if the wait period is 250ms, then the callback
Chris@0:  *   will only be called at most 4 times per second.
Chris@0:  * @param {bool} immediate
Chris@0:  *   Whether we wait at the beginning or end to execute the function.
Chris@0:  *
Chris@0:  * @return {function}
Chris@0:  *   The debounced function.
Chris@0:  */
Chris@17: Drupal.debounce = function(func, wait, immediate) {
Chris@0:   let timeout;
Chris@0:   let result;
Chris@17:   return function(...args) {
Chris@0:     const context = this;
Chris@17:     const later = function() {
Chris@0:       timeout = null;
Chris@0:       if (!immediate) {
Chris@0:         result = func.apply(context, args);
Chris@0:       }
Chris@0:     };
Chris@0:     const callNow = immediate && !timeout;
Chris@0:     clearTimeout(timeout);
Chris@0:     timeout = setTimeout(later, wait);
Chris@0:     if (callNow) {
Chris@0:       result = func.apply(context, args);
Chris@0:     }
Chris@0:     return result;
Chris@0:   };
Chris@0: };