JSON.stringify of objects wrapped with JSAdapter gets an extra wrapper of quotes. The output of the sample program

function Foo() {
    var that = this;
    return new JSAdapter(Foo.prototype, {}, {
        __call__: function(name) {
            return that[name].call(that, arguments);
        }
    });
}
Foo.prototype.toJSON = function() {
    return '{}';
}
var f = new Foo();
console.log(JSON.stringify(f));

should be '{}' but is '"{}"'. Whatever the toJSON function returns is wrapped with an extra pair of double-quotes. The extra wrapping is unnecessary, the output of toJSON should be returned unmodified.