office js - In Excel Online, OfficeJS API is not passing the host_Info_ parameter anymore to Excel Add-In

Question

I don't know when this started happening or if things have changed but the _host_Info param is not being passed by the framework to my Excel Add-In in Excel Online.

It passes an empty "et=" parameter which is OK in this case since I'm in dev mode. The Excel desktop client is still passing it.

This is required by my add-ins to switch functionality between Excel Online and Excel for Windows.

I've checked the docs and can't find that anything has changed.

Answer 1

To append to Sudhi's answer: with the official API coming as per the link in Sudhi's answer, we've gone ahead and also added a "shim" for the API in the OfficeJsHelpers library.

The shim still uses the workaround code that Sudhi mentions -- window.sessionStorage['hostInfoValue'] -- but it wraps it in an API very similar to what is coming in the official Office.js. Once the official API is available, we'll switch the shim code to make use of that instead. The beauty of this approach is that if you use OfficeJsHelpers via an NPM package, all you have to do is update your package dependency, and you'll suddenly go from an unofficial and potentially-fragile workaround to an API that relies on 100% officially-exposed properties -- all without changing your own code! Likewise, if at that time you decide to switch back to using the official Office.js version, the similarity of the APIs (essentially just namespace differences) should make it trivial to switch over the implementations.

The helper APIs are OfficeHelpers.Utilities.host (which will return WORD, EXCEL, etc.) and OfficeHelpers.Utilities.platform (which will return IOS, PC, OFFICE_ONLINE, or MAC). The constants are defined in OfficeHelpers.HostType and OfficeHelpers.PlatformType.

You can find the NPM package at https://www.npmjs.com/package/@microsoft/office-js-helpers, and either install it via NPM, or use a CDN like Unpkg to quickly try it out: https://unpkg.com/@microsoft/office-js-helpers@0.4.2/dist/office.helpers.min.js

console.log(OfficeHelpers.Utilities.host);
console.log(OfficeHelpers.Utilities.platform);

if (OfficeHelpers.Utilities.platform === OfficeHelpers.PlatformType.OFFICE_ONLINE) {
    console.log("Yep, I'm on the web client");
}

I hope you find the above helpful as an interim measure, and we'll be sure to update this StackOverflow thread (and the OfficeJsHelpers code) once the official API is released.