Added debounce for typeahead search optimization

.eslintrc

@@ -9,6 +9,9 @@ env:
   jquery: true
   node: true
 
+parseOptions:
+  sourceType: "module"
+
 # http://eslint.org/docs/rules/
 rules:
   # Possible Errors

app/assets/javascripts/debounce.js

@@ -0,0 +1,18 @@
+// 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.
+export function debounce(func, wait, immediate) {
+	var timeout;
+	return function() {
+		var context = this, args = arguments;
+		var later = function() {
+			timeout = null;
+			if (!immediate) func.apply(context, args);
+		};
+		var callNow = immediate && !timeout;
+		clearTimeout(timeout);
+		timeout = setTimeout(later, wait);
+		if (callNow) func.apply(context, args);
+	};
+};

app/assets/javascripts/restful_typeahead.js

@@ -4,13 +4,13 @@
   search API and the UI components.
   Documentation here: https://github.com/bassjobsen/Bootstrap-3-Typeahead
 **/
+import { debounce } from './debounce.js';
 
 $(function() {
-  $('input.search-query.typeahead').each(function(i, el){
+  $('input.search-query.typeahead').each(debounce(function(i, el){
     var typeahead = $(el).typeahead({
       items: 10,
       minLength: 3,
-      delay: 350,
       showCategoryHeader: true,
       autoSelect: false,
       source: function (query, process) {
@@ -46,5 +46,5 @@ $(function() {
                  showAll: true
                }
     });
-  });
+  }, 350));
 });