Add User Defined function support to the Apps for Office Excel APIs so that users can enter formulas in excel. User Defined Functions are one of the most powerful features of Excel (and some competitor spreadsheets products now available in the web). They are critical for us to make our Apps for Office product as powerful as our legacy on premise product.

Similar to Document.SelectionChanged event, the following Workbook-level events would be useful to have exposed via the JavaScript API (in no particular order):

Activate,Deactivate
BeforeSave,AfterSave
BeforeClose
Shutdown
SheetActivate,SheetDeactivate
SheetBeforeDoubleClick
SheetBeforeRightClick
SheetChange
SheetSelectionChange

Extend the getFileAsync functionality to work on Excel as well. It's essential in order to be able to export the file to a web service.

Since there is no way to cancel the changes made by an add-in, we need to provide users with backup options.

The current version of JavaScript API for Excel doesn't have a method for copying a sheet with its data and formatting, there are no elegant and fast workarounds available.

Could you please let us know if it's possible to add this method to JavaScript API for Excel?

We have a requirement to load a workbook from a remote source from within the add-in. User logs in, selects from a list and workbook template loads.

With the Word JS API we can load a template remotely using an AJAX call that returns the workbook as a base64 string and then insert the response into the current workbook using the replace option. AFAIK this doesn't exist for the Excel API and we download the workbook and then instruct the user to open from the download pane.

You can try to run this code and check the Undo/Redo stack:
Excel.run(function (ctx) {
return ctx.sync();
});

We would like to have array formula support available in the office.js API. We use these heavily in our VSTO Excel Add-in in combination with user defined functions to display function output in multiple cells. Having this feature available would allow us to build the Excel Office Add-in we would like to build.

For other forum browsers, here is an example of an array formula.
https://www.ablebits.com/office-addins-blog/2015/02/25/array-formulas-functions-excel/#array-formula-intro

Please note that while Binding.setDataAsync() in the office.js API supports adding formulas to a range of cells, you cannot see or edit the formula after adding.

Please add the ability to create, delete, and modify Excel Comments on specific cells using Office.js

Create a function to bring in cell Comments into an app create using JavaScript API, to bring in Comments explaining a value. If I create a visualization app in Excel, for example and there are outliers in the data. The users can Insert comment into Excel cell and the app can add it into the visualization.

We have a need to repeat the same formatted Worksheet over and over based on selections made by the user. It would be great to setup a template so that same worksheet can be copied. The worksheet has all formatting including printing stuff in place already. Be great to just be able to copy that and fill in the data.

The ability to update, delete and insert into the Named Item Collection items for excel named ranges.

The enhanced Excel-specific APIs available for developing Office Add-ins that run with Excel 2016 are a nice start. There are some key missing APIs. One area in need of extending is eventing. For workbooks that contain multiple worksheets, it is critical for the Add-in to be able to determine when a worksheet is activated/deactivated so that the Add-in's UI can adapt accordingly. Similarly, the Office Add-in should be able to hook an event so that when the workbook gets closed/shut down (and maybe Saved), the Add-in can persist in-memory state into the workbook.

In the current version of the office javascript api I can see that the setSelectedDataAsync method allow only inserting text, matrix and table into excel spreadsheet.

I would like to see the javascript api enhanced and allow inserting pivot Table also. In this way I can use pivot Table helpers (such as slicer, fields list ....) and also refresh pivot table programmatically.

The current BindingDataChangedEventArgs object passed to the event handler for the Binding.BindingDataChanged event only contains properties for the binding that raised the event and the type of event. There is no specific information about what cells, columns, or rows in the table object were changed. When dealing with tables with many rows and columns and/or end-user gestures that edit/insert/delete many cells/rows/columns at once, this API is not very useful. Contrast this to the (Excel) COM APIs where, at least, the SheetChanged event provides a Range object that describes what was changed.

Enhance the Office JavaScript APIs (for Excel 2016+) to expose a mechanism (perhaps a Validation relationship or property) that allows the developer to configure a cell so that the end-user selects the value for the cell by picking from a list of values. The list of values might be specified by some other range. In a VSTO add-in (and native Excel) this can be achieved by configuring the Data Validation properties on a cell/range.

There should be a way to open a external excel workbook by providing URL for that file on excel online via officejs. so that user can open a template stored on some other server which contains desired formatting and named-ranges which can be modified on Excel Online

The ability to edit conditional formatting in OfficeJS Excel API.

Having the ability to create custom pivots programmatically would be useful feature for reporting latest data for better user experience.

Enable Visual Studio Mac to use the VBA hierarchy.
This will enable VB.Net to automate Excel Mac.
This will provide a relatively painless, powerful migration path for VBA devs.