`.constructor` is unreliable, and can be easily forged - of course, `Symbol.typeof` would create the same unreliability with one of the few truly reliable operators in the language.
On Tue, Jan 15, 2019 at 12:38 PM J Decker <[email protected]> wrote: > > > On Sat, Jan 12, 2019 at 8:19 AM Randy Buchholz <[email protected]> > wrote: > >> (Hi all, new to group) >> >> >> >> Some of the Well Known Symbols are linked to standard functions – >> Symbol.toStringTag - A string value used for the default description of an >> object. Used by Object.prototype.toString(). >> >> >> >> When I have a Class instance (say, `const flow = new Flow()`, the >> debugger shows `flow = Flow {`. >> >> But when I do `console.log( typeof flow)` the output is `object`. >> >> >> >> I assume changing basic behavior `typeof` would be breaking, but >> extending it through a symbol would be useful. >> >> >> >> `Symbol.typeofTag` of just `Symbol.typeof` >> >> >> >> Invoking `typeof` on an object with this symbol would return “user-typed” >> information. >> >> >> > > can't you just use the constructor name when needing more detail? > > var a = new Date(); > a.constructor.name > "Date" > > > >> (Posting Question) >> >> What is the preferred format/approach for highlighting code in posts? >> >> ____________________ >> >> Possible Approaches >> >> ``` >> >> class Flow { >> >> get [Symbol.typeof]() { return Flow; } or { return “Flow” } >> >> } >> >> ``` >> >> would work much like Symbol.species. Implicitly casting to string would >> be more intuitive I think. >> >> >> >> Other approaches, (special handling of well-knowns) could be: >> >> >> >> Decorator-ish >> >> ``` >> >> [Symbol.typeof] = “Flow” >> >> Class Flow {… >> >> ``` >> >> or inferred >> >> >> >> ``` >> >> [Symbol.typeof] >> >> class Flow {… >> >> ``` >> >> >> >> Internal – In class, but not in a function. >> >> >> >> ``` >> >> Class Flow { >> >> [Symbol.typeof] >> >> or >> >> [Symbol.typeof] = “Flow” >> >> or >> >> [Symbol.typeof] = Flow >> >> or >> >> [Symbol.typeof] = this >> >> >> >> ``` >> >> >> >> Constructor >> >> ``` >> >> Class Flow { >> >> Constructor() { >> >> this[Symbol.typeof] = … >> >> … >> >> ``` >> >> >> _______________________________________________ >> es-discuss mailing list >> [email protected] >> https://mail.mozilla.org/listinfo/es-discuss >> > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss >
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