Unlike the desktop Excel APIs, which contain a "Precedents" and a "Dependents" on the Range object, the short answer is no for the Excel Javascript APIs, which brings me here. 

Is there a way or third-party piece of code to circumvent this huge lack from Microsoft ? If I can't navigate the formula tree, there is just not much useful I can add in terms of add-ins for Excel Online.

[Javascript API for Excel](https://dev.office.com/docs/add-ins/develop/understanding-the-javascript-api-for-office)

[Office Online](https://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwijntbx_7TXAhXGHxoKHTBsDRkQFggoMAA&url=https%3A%2F%2Foffice.live.com%2Fstart%2FExcel.aspx&usg=AOvVaw3PoFphSHilDRux1Y6zlukN)

UPDATE: to add some context, I've been writing auditing add-ins in C# in the past, to evaluate formula complexity, perform advanced reconciliation of formulas, reconstruct formulas differently, etc... I'm trying to convert a small piece of it, as a javascript prototype add-in, to see whether Excel online can handle it.