desired.output.js

                parsed_idl.members.forEach(function(member) {
                    this.members[parsed_idl.name].members.push(
                        new IdlInterfaceMember(member)
                    );
                }.bind(this));

prettier.output.js

                parsed_idl.members.forEach(
                    function(member) {
                        this.members[parsed_idl.name].members.push(
                            new IdlInterfaceMember(member)
                        );
                    }.bind(this)
                );

What I'd really like this whole thing to look like

                parsed_idl.members.forEach(member => {
                    let members = this.members[parsed_idl.name].members;
                    members.push(new IdlInterfaceMember(member));
                });