Error-free deep property access?
in [JavaScript]
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From: Matt Kruse on 11 May 2010 13:31 On May 11, 12:19 pm, Scott Sauyet <scott.sau...(a)gmail.com> wrote: > So this won't allow, for instance, > $props("myObj.prop1.prop2[current.value]") > Is that right? It needs to have only a single root at the first > token. That will cover a lot of possibilities, but the more general > case is interesting too. True. But since you're passing in a string, couldn't you just do: $prop("myObj.prop1.prop2."+current.value) ? Matt
From: Thomas 'PointedEars' Lahn on 11 May 2010 14:03 Matt Kruse wrote: > On May 11, 12:19 pm, Scott Sauyet <scott.sau...(a)gmail.com> wrote: >> So this won't allow, for instance, >> $props("myObj.prop1.prop2[current.value]") >> Is that right? It needs to have only a single root at the first >> token. That will cover a lot of possibilities, but the more general >> case is interesting too. > > True. But since you're passing in a string, couldn't you just do: > > $prop("myObj.prop1.prop2."+current.value) > ? Generally, no. Think about it. See also the caveats that I have mentioned. PointedEars -- Anyone who slaps a 'this page is best viewed with Browser X' label on a Web page appears to be yearning for the bad old days, before the Web, when you had very little chance of reading a document written on another computer, another word processor, or another network. -- Tim Berners-Lee
From: Scott Sauyet on 11 May 2010 14:06 Matt Kruse wrote: > On May 11, 12:19 pm, Scott Sauyet <scott.sau...(a)gmail.com> wrote: > >> So this won't allow, for instance, >> $props("myObj.prop1.prop2[current.value]") >> Is that right? It needs to have only a single root at the first >> token. That will cover a lot of possibilities, but the more general >> case is interesting too. > > True. But since you're passing in a string, couldn't you just do: > > $prop("myObj.prop1.prop2."+current.value) > ? Sure, unless current is undefined, which I think is the original problem we're trying to solve. :-) And of course we could want $props("myObj.prop1.prop2[current.deeply.nested.value]") as well. -- Scott
From: Thomas 'PointedEars' Lahn on 11 May 2010 14:39 Scott Sauyet wrote: > Matt Kruse wrote: >> On May 11, 12:19 pm, Scott Sauyet <scott.sau...(a)gmail.com> wrote: >>> So this won't allow, for instance, >>> $props("myObj.prop1.prop2[current.value]") >>> Is that right? It needs to have only a single root at the first >>> token. That will cover a lot of possibilities, but the more general >>> case is interesting too. >> >> True. But since you're passing in a string, couldn't you just do: >> >> $prop("myObj.prop1.prop2."+current.value) >> ? > > Sure, unless current is undefined, [...] Wrong. Think about what would happen with current.value = 42; or current.value = "foo.bar"; or current.value = "foo['bar']"; PointedEars -- Danny Goodman's books are out of date and teach practices that are positively harmful for cross-browser scripting. -- Richard Cornford, cljs, <cife6q$253$1$8300dec7(a)news.demon.co.uk> (2004)
From: Thomas 'PointedEars' Lahn on 11 May 2010 14:45
Matt Kruse wrote: > if ( p.match(/(.+?)(\[\d+\].*)/) ) { > p = RegExp.$1; > props.unshift(RegExp.$2); Other flaws of this approach that I have already mentioned aside, the `$n' properties of `RegExp' are deprecated as of JavaScript 1.5 at least. Use the return values of String.prototype.match() and RegExp.prototype.exec(), respectively, instead. <https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Deprecated_Features#RegExp_Properties> PointedEars -- Anyone who slaps a 'this page is best viewed with Browser X' label on a Web page appears to be yearning for the bad old days, before the Web, when you had very little chance of reading a document written on another computer, another word processor, or another network. -- Tim Berners-Lee |