meaning of push: function in javascript

Question

What is the meaning of return { push:function ..... in below code snippet. When I googled I found that push() method adds new items to the end of an array, and returns the new length. So I am not sure what is push:. It seems to be some kind of syntax. Can someone please explain me.

 function(notificationsArchive) { var MAX_LEN = 10; var notifications = []; return { push: function(notification) { var notificationToArchive; var newLen = notifications.unshift(notification); //push method can rely on the closure scope now! if (newLen > MAX_LEN) { notificationToArchive = this.notifications.pop(); notificationsArchive.archive(notificationToArchive); } }, // other methods of the NotificationsService }; 

Answer 1

The method push you are referencing has nothing to do with push with Arrays, it is a public method exposed by the module pattern. It only exposes methods and properties that the author of the code wants you to be able to call/set. It hides the variables MAX_LEN and notifications so they can not be changed from outside.

References on OO Module patterns:

• http://addyosmani.com/resources/essentialjsdesignpatterns/book/#modulepatternjavascript
• http://www.raymondcamden.com/2013/05/13/JavaScript-Design-Patterns-The-Revealing-Module-Pattern

Answer 2

 function(notificationsArchive) { var MAX_LEN = 10; var notifications = []; return { push: function(notification) { var notificationToArchive; var newLen = notifications.unshift(notification); //push method can rely on the closure scope now! if (newLen > MAX_LEN) { notificationToArchive = this.notifications.pop(); notificationsArchive.archive(notificationToArchive); } }, // other methods of the NotificationsService };