diff core/misc/debounce.es6.js @ 0:c75dbcec494b

Initial commit from drush-created site

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/core/misc/debounce.es6.js	Thu Jul 05 14:24:15 2018 +0000
@@ -0,0 +1,48 @@
+/**
+ * @file
+ * Adapted from underscore.js with the addition Drupal namespace.
+ */
+
+/**
+ * Limits the invocations of a function in a given time frame.
+ *
+ * The debounce function wrapper should be used sparingly. One clear use case
+ * is limiting the invocation of a callback attached to the window resize event.
+ *
+ * Before using the debounce function wrapper, consider first whether the
+ * callback could be attached to an event that fires less frequently or if the
+ * function can be written in such a way that it is only invoked under specific
+ * conditions.
+ *
+ * @param {function} func
+ *   The function to be invoked.
+ * @param {number} wait
+ *   The time period within which the callback function should only be
+ *   invoked once. For example if the wait period is 250ms, then the callback
+ *   will only be called at most 4 times per second.
+ * @param {bool} immediate
+ *   Whether we wait at the beginning or end to execute the function.
+ *
+ * @return {function}
+ *   The debounced function.
+ */
+Drupal.debounce = function (func, wait, immediate) {
+  let timeout;
+  let result;
+  return function (...args) {
+    const context = this;
+    const later = function () {
+      timeout = null;
+      if (!immediate) {
+        result = func.apply(context, args);
+      }
+    };
+    const callNow = immediate && !timeout;
+    clearTimeout(timeout);
+    timeout = setTimeout(later, wait);
+    if (callNow) {
+      result = func.apply(context, args);
+    }
+    return result;
+  };
+};