On Fri, Nov 9, 2012 at 11:57 AM, Domenic Denicola < [email protected]> wrote:
> The idea is to not do the processing if the JSON parsing fails.**** > > ** ** > > *From:* Cryptic Swarm [mailto:[email protected]] > *Sent:* Friday, November 9, 2012 11:55 > *To:* Domenic Denicola > *Cc:* [email protected] > *Subject:* Re: then**** > > ** ** > > The following should work? Finally expects a block statement, so need to > wrap it in { }...**** > > ** ** > > var info, processed; > try { > info = JSON.parse(json); > } catch (exception) { > console.log("Information JSON malformed."); > } finally { try { > processed = process(info); > } catch (exception) { > console.log("Error processing information."); > }}**** > > On Fri, Nov 9, 2012 at 1:46 PM, Domenic Denicola < > [email protected]> wrote:**** > > The recent promise discussion prompted me to recall the following > musing/proposal from Kris Kowal: > > https://github.com/kriskowal/q/wiki/On-Exceptions > > In short, there's a common code pattern that you can do with promises that > you can't do with synchronous code. The proposal is for a language > extension `then` that would allow synchronous code like this: > > var info, processed; > try { > info = JSON.parse(json); > } catch (exception) { > console.log("Information JSON malformed."); > } then { > processed = process(info); > } catch (exception) { > console.log("Error processing information."); > } > > Since seeing this, I've run into a lot of situations where a `then` would > come in handy. I wanted to see if anyone else thought this was a great > idea, and if it has any chance as an ES7-level proposal. > > _______________________________________________ > 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 > > I believe you want that to desugar into: var info, processed; try { info = JSON.parse(json); try { processed = process(info); } catch (exception) { console.log("Error processing information."); } } catch (exception) { console.log("Information JSON malformed."); } ... which is the synchronous equivalent of callbacks marching ever rightward, and it is ugly and hard to read. Like deeply-nested if statements, it's more readable if you put it into the context of a function and follow an "early exit" coding style rather than a "only one exit" coding style: var info, processed; try { info = JSON.parse(json); } catch (exception) { console.log("Information JSON malformed."); return; } try { processed = process(info); } catch (exception) { console.log("Error processing information."); return; } This still breaks up the "normal" flow of the function, but I don't see this as significantly less readable than the proposed try/catch/then.
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