Originally reported by @MJKWoolnough in PR #391, this issue is still valid:

Found a bug in how $externalize converts structs to js objects.

It occurs when you have an empty struct, searchJsObject doesn't handle the case where there are no fields to check.

This can be shown by just printing an empty struct{} to the log: -

http://www.gopherjs.org/playground/#/PfMcT_bbbz

The output of that program is:

panic: Cannot read property 'prop' of undefined

Expect it to be no panic, and logging an object without any fields to console.