We are using SharePoint 2016 on-premise. MDS (Minimal Download Strategy) is activated as default. Several .aspx pages contain JSOM functions are running fine there.

One day, we want to test the behavior by inactivate MDS (by manage site feature -> inactivate, not by PowerShell). After test and reactivate (by manage site feature -> activate, not by PowerShell), several JSOM pages (but not all) are not working.

In console log it said:

sp.js (2,260901)  Unable to get property 'toUpperCase' of undefined or null reference

Is it because MDS feature cannot be reversed after inactivate? Any advice?

  • Try adding debugger in sp.js file at the line where you are getting this error. check on which null variable it is calling toUpperCase function. – Ganesh Sanap Jul 24 at 4:47

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