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This went out on FB and Twitter. I guess people who came from there weren't HN users. Hopefully they are now. I agree about the comment quality though, I was h

This went out on FB and Twitter. I guess people who came from there weren't HN users. Hopefully they are now. I agree about the comment quality though, I was hoping for a discussion about the idea itself.

blowski 13y ago
The idea is good, but I can't see why I would switch to this from Q.js. The latter is: * pretty lightweight (9.8KB) * well-supported, with very active development (10 commits in the last month) * good documentation You need to explain the benefits of .andthen() in comparison to Q.js, because at the moment it just looks like another promises JS framework.
- aravindet 13y ago
  I think the benefit is primarily a simpler API and nicer syntax for most of the things you'd want to do. For instance with Q.all, you'd do with: return Q.all([ eventualAdd(2, 2), eventualAdd(10, 20) ]).then(function(values) { console.log(values[0], values[1]); }); can instead be eventualAdd(2, 2). and(eventualAdd(10,20)). then(function(a, b) { console.log(a, b); }); which I feel reads nicer and gives you the results in a more usable form (something that would require another call, Q.spread, in Q). This also allows complex composition. Say you want to run 4 functions A, B, C and D, such that A and B are called together, C is called when A returns, then D is called when B and C both return. This is clumsy to do on Q, requiring packing promises into an array, etc. The other big thing is error handling. In Q, if you forget to set an error handler at the end of the chain or explicitly set the default handler with .done(), errors go unhandled. This is clumsy; in fact the Q documentation says: "This is a stopgap. We are exploring ways to make unhandled errors visible without any explicit handling." We've implemented this in andthen. If there's no error handler and execution reached the end of the chain, it will be thrown so Node or the browser will print it. There's fulfilment as well, but I get your point about putting this better in the README.
  - jhrobert 13y ago
    This behaviour is not promise/a compatible. Make it optional and you become promise/a compatible.

blowski 13y ago

The idea is good, but I can't see why I would switch to this from Q.js. The latter is: * pretty lightweight (9.8KB) * well-supported, with very active development (10 commits in the last month) * good documentation You need to explain the benefits of .andthen() in comparison to Q.js, because at the moment it just looks like another promises JS framework.

aravindet 13y ago
I think the benefit is primarily a simpler API and nicer syntax for most of the things you'd want to do. For instance with Q.all, you'd do with: return Q.all([ eventualAdd(2, 2), eventualAdd(10, 20) ]).then(function(values) { console.log(values[0], values[1]); }); can instead be eventualAdd(2, 2). and(eventualAdd(10,20)). then(function(a, b) { console.log(a, b); }); which I feel reads nicer and gives you the results in a more usable form (something that would require another call, Q.spread, in Q). This also allows complex composition. Say you want to run 4 functions A, B, C and D, such that A and B are called together, C is called when A returns, then D is called when B and C both return. This is clumsy to do on Q, requiring packing promises into an array, etc. The other big thing is error handling. In Q, if you forget to set an error handler at the end of the chain or explicitly set the default handler with .done(), errors go unhandled. This is clumsy; in fact the Q documentation says: "This is a stopgap. We are exploring ways to make unhandled errors visible without any explicit handling." We've implemented this in andthen. If there's no error handler and execution reached the end of the chain, it will be thrown so Node or the browser will print it. There's fulfilment as well, but I get your point about putting this better in the README.
- jhrobert 13y ago
  This behaviour is not promise/a compatible. Make it optional and you become promise/a compatible.