Python dir() equivalent in JavaScript?

You could use Object.keys(), e.g.:

> Object.keys(window)
["top", "window", "location", "external", "chrome", "Intl", "v8Intl", "document", "$", "jQuery", "MSIsPlayback", "i", "prepareEditor", "StackExchange", "scriptSrc", "careers_adurl", "careers_cssurl", "careers_leaderboardcssurl", "careers_companycssurl", "careers_adselector", "_gaq", "_qevents", "jQuery171008060155878774822", "__qc", "quantserve", "uh", "_gat", "gaGlobal", "gauth", "genuwine", "moveScroller", "styleCode", "sanitizeAndSplitTags", "initTagRenderer", "showFadingHelpText", "initFadingHelpText", "profileLink", "EventEmitter", "votesCast", "tagRendererRaw", "tagRenderer", "ytCinema", "IN_GLOBAL_SCOPE", "prettyPrintOne", "prettyPrint", "PR_SHOULD_USE_CONTINUATION", "PR", "Markdown", "apiCallbacks"]