Office JavaScript APIs
The JavaScript API for Office enables you to create web applications that interact with the object models in Office host applications. Your application will reference the office.js library, which is a script loader. The office.js library loads the object models that are applicable to the Office application that is running the add-in.
The NPM package for Office.js is a copy of what gets published to the official "evergreen" Office.js CDN, at https://appsforoffice.microsoft.com/lib/1/hosted/office.js. It NPM's beta packages also offer a channel for faster-cadence beta-testing (relative to the slower-cadence official BETA endpoint).
For more information on Office Add-ins and the Office JavaScript APIs, see: