On Sunday, January 6, 2013, Axel Rauschmayer wrote: > > Exactly Brendan, I could not agree more and this is my No. 1 pitfall > about JS: developers often not doing real work complaining about stuff that > developers doing real work don't even care about or never ever had to worry > about. > > I don’t follow. Who are these people not doing “real work”? And I don’t > think discussing the language qualifies as complaining. > > > In any case they can learn and understand the feature/problem using the > feature when needed, avoiding its weakness when necessary. > > > > About falsy and truthy, null and undefined, who cares ... seriously, and > to be honest, that's not a pitfall, is rather a feature when needed as it > is for all other scripting languages as long as you know what you are doing > ... and no programming language will save you if you don't know what you > are doing and it's your duty, as developer, to understand the language you > are using if that's your job. > > “Warts” is probably a better term than “pitfalls”. > > > Again, about falsy ... if I see a glass empty, it does not mean I used a > microscope to understand no water is left in the whole glass surface ... I > just consider that empty and I add water on top. > > > > Engineers have the tendency to over complicate even simple tasks as the > one I've just described ... what is the benefit? What is the result? That > the day falsy values in JS will disappear libraries authors will implement > an isFalsy(value) function/method and use it 90% of the time regretting the > trick with == disappeared ... isn't it ;-) > > What is the trick with ==? Note that == does not respect truthiness or > falsiness: > > > 2 == true > false > > 2 == false > false > > > '2' == true > false > > '2' == false > false
None of these (above) abstract comparison operations represents "truthy" or "falsy" behaviour. 0 == false; // true 11.9.3.7 converts to 0==0 "" == false; // true 11.9.3.7 converts to ""==0 11.9.3.5 converts to 0==0 1 == true; // true 11.9.3.7 converts to 1==1 "" becomes +0 per 9.3.1 +0 becomes false per 9.2 true becomes 1 per 9.3 table 12 The unary logical NOT ! also converts with ToBoolean. 2==true is just the number two compared with the Boolean true, which aren't equal in value or type and have no criteria for conversion. Rick > > > -- > Dr. Axel Rauschmayer > a...@rauschma.de > > home: rauschma.de > twitter: twitter.com/rauschma > blog: 2ality.com > > _______________________________________________ > es-discuss mailing list > es-discuss@mozilla.org > https://mail.mozilla.org/listinfo/es-discuss >
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