Debounce Autosave callback.

app/assets/javascripts/autosave.js

 /* eslint-disable no-param-reassign, prefer-template, no-void, consistent-return */
 
+import _ from 'underscore';
 import AccessorUtilities from './lib/utils/accessor';
 
 export default class Autosave {
@@ -13,7 +14,13 @@ export default class Autosave {
     this.key = 'autosave/' + key;
     this.field.data('autosave', this);
     this.restore();
-    this.field.on('input', () => this.save());
+    this.field.on('input', this.debounceInputHandler());
+  }
+
+  debounceInputHandler() {
+    return _.debounce(() => {
+      this.save();
+    }, Autosave.DEBOUNCE_TIMER);
   }
 
   restore() {
@@ -57,4 +64,6 @@ export default class Autosave {
   dispose() {
     this.field.off('input');
   }
+
+  static DEBOUNCE_TIMER = 300;
 }

spec/javascripts/autosave_spec.js

 import $ from 'jquery';
+import _ from 'underscore';
 import Autosave from '~/autosave';
 import AccessorUtilities from '~/lib/utils/accessor';
 
@@ -10,12 +11,24 @@ describe('Autosave', () => {
   describe('class constructor', () => {
     beforeEach(() => {
       spyOn(AccessorUtilities, 'isLocalStorageAccessSafe').and.returnValue(true);
+      spyOn(_, 'debounce');
+      spyOn(Autosave.prototype, 'save');
       spyOn(Autosave.prototype, 'restore');
+      autosave = new Autosave(field, key);
     });
 
-    it('should set .isLocalStorageAvailable', () => {
-      autosave = new Autosave(field, key);
+    it('should debounce the input handler', () => {
+      expect(_.debounce).toHaveBeenCalled();
+      expect(autosave.save).not.toHaveBeenCalled();
+
+      const [cb, timer] = _.debounce.calls.argsFor(0);
+      cb(); // execute debounced callback
 
+      expect(timer).toEqual(Autosave.DEBOUNCE_TIMER);
+      expect(autosave.save).toHaveBeenCalled();
+    });
+
+    it('should set .isLocalStorageAvailable', () => {
       expect(AccessorUtilities.isLocalStorageAccessSafe).toHaveBeenCalled();
       expect(autosave.isLocalStorageAvailable).toBe(true);
     });
@@ -59,12 +72,10 @@ describe('Autosave', () => {
 
         Autosave.prototype.restore.call(autosave);
 
-        expect(
-          field.trigger,
-        ).toHaveBeenCalled();
+        expect(field.trigger).toHaveBeenCalled();
       });
 
-      it('triggers native event', (done) => {
+      it('triggers native event', done => {
         autosave.field.get(0).addEventListener('change', () => {
           done();
         });
@@ -81,9 +92,7 @@ describe('Autosave', () => {
       it('does not trigger event', () => {
         spyOn(field, 'trigger').and.callThrough();
 
-        expect(
-          field.trigger,
-        ).not.toHaveBeenCalled();
+        expect(field.trigger).not.toHaveBeenCalled();
       });
     });
   });