Just a very quick and dirty stab at using JS for IDL (more at https://github.com/darobin/ideal/)

dom.js

var ideal = require("../ideal")
, dom = exports
;

dom.Phase = ideal.legacyEnum("NONE", "CAPTURING_PHASE", "AT_TARGET", "BUBBLING_PHASE");

dom.Event = ideal.class
                    .importLegacyEnum(dom.Phase)
                    .constructor
                        .param(String, "type")
                        .param({ bubbles: false, cancelable: false }, "options")
                    .nonwritable
                        .property(String, "type")
                        .property(dom.EventTarget, "target").nullable
                        .property(dom.EventTarget, "currentTarget").nullable
                        .property(dom.Phase, "eventPhase")
                        .property(Boolean, "bubbles")
                        .property(Boolean, "cancelable")
                        .property(Boolean, "defaultPrevented")
                        .property(Boolean, "isTrusted").nonconfigurable
                        .property(Date, "timeStamp")
                    .method(null, "preventDefault")
                    .method(null, "initEvent")
                        .param(String, "type")
                        .param(Boolean, "bubbles")
                        .param(Boolean, "cancelable")
;

dom.CustomEvent = ideal.class
                            .extends(dom.Event)
                            .constructor
                                .param(String, "type")
                                .param({bubbles: false, cancelable: false, detail: null}, "options")
                            .method(null, "initCustomEvent")
                                .param(String, "type")
                                .param(Boolean, "bubbles")
                                .param(Boolean, "cancelable")
                                .param(ideal.any, "details")
;

dom.EventTarget = ideal.interface
                            .method(null, "addEventListener")
                                .param(String, "type")
                                .param(dom.EventListener, "callback").nullable
                                .param(Boolean, "capture").default(false)
                            .method(null, "removeEventListener")
                                .param(String, "type")
                                .param(dom.EventListener, "callback").nullable
                                .param(Boolean, "capture").default(false)
                            .method(Boolean, "dispatchEvent")
                                .param(dom.Event, "event")
;

// TODO: Deal with this craziness
dom.EventListener = ideal.interface;

dom.Content = ideal.union(dom.Node, String);

dom.ParentNode = ideal.interface
                        .nonwritable
                            .property(dom.HTMLCollection, "children")
                            .property(dom.Element, "firstElementChild").nullable
                            .property(dom.Element, "lastElementChild").nullable
                            .property(Number, "childElementCount")
                        .method(null, "prepend")
                            .param(dom.Content, "nodes").variadic
;

dom.ChildNode = ideal.interface
                        .nonwritable
                            .property(dom.Element, "previousElementSibling").nullable
                            .property(dom.Element, "nextElementSibling").nullable
                        .method(null, "before")
                            .param(dom.Content, "nodes").variadic
                        .method(null, "after")
                            .param(dom.Content, "nodes").variadic
                        .method(null, "replace")
                            .param(dom.Content, "nodes").variadic
                        .method(null, "remove")
;

dom.MutationCallback = ideal.callback(null)
                                .param([dom.MutationCallback], "mutations")
                                .param(dom.MutationObserver, "observer")
;