I try to create an app by sharepoint framework for MS Project. By using JSOM I need to add some referens for PS.JS Which I don't know how to do it.
You only need to load manually the PS.js inside the web part, here's the code:
SP.SOD.registerSod('PS.ProjectContext', SP.Utilities.Utility.getLayoutsPageUrl('ps.js'));
SP.SOD.loadMultiple(['PS.ProjectContext'], <your function>);
First line register the namespace and set the url where the ps.js reside; second line load the javascript.
This approach function correctly when the web part is already inside the web part page. If you are working with the local workbench you also need to load the Sharepoint javascript files.