The way that a nil *js.Object is printed is different than the way that a nil user-defined struct is printed. I ran into this when attempting to use fmt.Sprintf("%+v", someJSObject) for test comparison purposes.

For example, this program on the playground (https://gopherjs.github.io/playground/#/MP9gVpB6AP):

package main

import (
	"fmt"

	"github.com/gopherjs/gopherjs/js"
)

type Object struct{}

func main() {
	fmt.Println("Printing a nil *Object (regular struct):")
	a := struct {
		o *Object
	}{}
	fmt.Printf("a.o: %+v\n", a.o)
	fmt.Printf("a: %+v\n", a)

	fmt.Println("\nPrinting a nil *js.Object:")
	b := struct {
		o *js.Object
	}{}
	fmt.Printf("b.o: %+v\n", b.o)
	fmt.Printf("b: %+v\n", b)
}

Produces:

Printing a nil *Object (regular struct): 
a.o: <nil> 
a: {o:<nil>} 
 
Printing a nil *js.Object: 
b.o: null 
b: {o:0x1} 

i.e. a nil *js.Object is printed as null instead of nil on its own, and when inside a struct it is printed as 0x1 despite being nil.