Fix input search lag via debounced keyup function (#3491)

* Create debounce function, switch jets to manual search mode, debounce .keyup on the input box

* Edit comment

js/app.js

@@ -30,7 +30,7 @@ $(window).resize(function () {
 
 var isSearching = false;
 var jets = new Jets({
-  searchTag: '#jets-search',
+  callSearchManually: true,
   contentTag: '.jets-content',
   didSearch: function (searchPhrase) {
     document.location.hash = '';
@@ -78,6 +78,14 @@ var jets = new Jets({
   }
 });
 
+// Wrap the jets.search function with a debounced function
+var debouncedSearch = debounce(function(e) {
+  jets.search(e.target.value);
+}, 350);
+
+// Attach a keyup event listener to the input
+$('#jets-search').keyup(debouncedSearch);
+
 /**
  * Ensure searching is conducted with regard to the user's viewport
  * after re-sizing the screen and close all categories after re-sizing
@@ -139,3 +147,27 @@ function closeCategory(category) {
   $('.' + category + '-table').css('display', 'none');
   document.location.hash = '';
 }
+
+/**
+ * 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.
+ * 
+ * @param func The function to be debounced
+ * @param wait The time in ms to debounce 
+ */
+function debounce(func, wait) {
+  var timeout;
+
+	return function() {
+		var context = this, args = arguments;
+		var later = function() {
+			timeout = null;
+			func.apply(context, args);
+    };
+
+		clearTimeout(timeout);
+		timeout = setTimeout(later, wait);
+		if (!timeout) func.apply(context, args);
+	};
+};