Hello, sharez, you wrote: S> In that case all setTitle (), setColor () inside besides DOM-tree change should will also check, whether it is created - too quite good such complication, especially, if such methods much (and them much). Complexity not such and big, and it is faster a question of requirements. If we want to have such properties - anyway to check. It is possible certainly and not to check and always to change/read from DOM, but, , possibility is more favourable. (*) S> the main idea was that it is convenient to create this.el with all inner pattern without to a DOM-tree of immediately document, and to add it only by an explicit call, somehow so: Not-not-not, binding of object and DOM an element it already also is that . Only, with a difference that the element is under construction . S> Thus to us prevents to set nothing already at a stage of a call of the designer Title, Color in a tree stored in an internal field this.el. It is possible even to do addEventListener/removeEventListener. Prevents: how them to set if conditional createElement is not caused yet? We are returned to the beginning (*), and equally it is necessary to all of us it is created or not in . If speech about the job only values by default - that of objects-templates/parameters helps with successors. Besides, setting of new values by default in successors - the bad variant in itself: it is in places it can be unexpected (no less than on the contrary). Actually where it is more interesting that to do if the successor wants to give the DOM tree, and basic setTitle not virtual and writes the text not there. And in the ending - chain Control - Button is difficult in itself. I mean that Control will be terribly overloaded anyway, and there will be all bound classes at once (and those which not button too). I did to myself Button and LinkButton, but LinkButton installed only a basic name of style (to be exact a prefix). And here in process such from 10-15 - this canoe time and again, and as a result came to that directly I in all the same did not create them, and created on the basis of a template (dom tree) where elements (we tell xcontrol) were uncovered in already present dom. And the code already addressed to them on names. I to that am what well here I do not see necessity of considered possibility for the life of me. Or we know in advance property sets/values and we can freely transfer them in the designer, or we use after. In the designer can be quite used - after all while the element not - to break there is nothing (certainly, if properties not virtual). Besides, it is not necessary and to forget that DOM is always , therefore the approach: changes only through instead of in DOM directly works a little bit better. (After all over it it is necessary still to construct, so after all?) . In general, I will finish perhaps that I at faith level consider that the base class should not cause the successor. But, I admit that occasionally in with me cases in I sin. And to create convenient - challenging task. Good luck in it. By the way half modern with ease do sheet and there and then somewhere in the most inconvenient place. S> unfortunately, with Google Closure Tools I not a sign, but will look at a leisure. Without fanaticism only, the code + the long history there is a lot of. Examples can are loaded long since not compiled js consists from big kol-va units/files. But they (units) there at least are... Instead of profanation as in TS. I not with all there agree, but inspiration in due time obtained and much. Especially system of units and disposable (in ) it was pleasant. Which that from ideas transferred also to itself. It seems to me it is the most adult dial-up , but JS repels, and for their compiler it is necessary also correctly to write it. And really normal editors are not present, props everywhere one.