ES3 protobuf - getRepeatedWrapperField & wrapRepeatedField_

I am trying to run protbuf serialization for JScript app that runs in a window scripting host runtime (WSH) on window. The JScript seems to based on a very old version of Ecmascript.

I webpacked my app code and ran into following error

"length is null or not an object"

for this line

for (var d = jspb.Message.getRepeatedField(a, c), e = [], f = 0; f < d.length; f++)

This seeems to be happening inside wrapRepeatedField_ function from a getRepeatedWrapperField call.

The same webpacked application code runs perfectly fine on chrome browser. So I am suspecting an issue either with missing polyfills because of which the message was not initialized properly.

I would appreciate any hints on how I could make this work on this old JScript runtime.