An Excel add-in interacts with objects in Excel by using the Office JavaScript API, which includes two JavaScript object models:
Excel JavaScript API: These are the application-specific APIs for Excel. Introduced with Office 2016, the Excel JavaScript API provides strongly-typed objects that you can use to access worksheets, ranges, tables, charts, and more.
Common APIs: Introduced with Office 2013, the Common API can be used to access features such as UI, dialogs, and client settings that are common across multiple types of Office applications.
This section of the documentation focuses on the Excel JavaScript API, which you'll use to develop the majority of functionality in add-ins that target Excel on the web or Excel 2016 or later. For information about the Common API, see Common JavaScript API object model.
Use Script Lab to get started quickly with a collection of built-in samples that show how to complete tasks with the API. You can run the samples in Script Lab to instantly see the result in the task pane or worksheet, examine the samples to learn how the API works, and even use samples to prototype your own add-in.