4 ms·

Could you elaborate? Coming from Lua I always found the nesting of anonymous functions messy and wondered why they weren't done as in the article.

awjr 10y ago
Promises and, more recently, Observables. Simply put: A promise resolves to a single value asynchronously, an observable resolves to (or emits) multiple values asynchronously (over time). Taken from here: http://stackoverflow.com/questions/36064303/what-are-the-differences-between-observables-and-promises-in-javascript http://stackoverflow.com/questions/36064303/what-are-the-dif...
- awjr 10y ago
  Oh I also forgot async/await "The purpose of async/await functions are to simplify the behavior of using promises synchronously and to perform some behavior on a group of Promises. Just like Promises are similar to structured callbacks, async/await is similar to combining generators and promises." https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...
Kiro 10y ago
Promises and async/await. This page is so outdated it shouldn't exist.
- mromanuk 10y ago
  He addressed more modern solutions at the bottom. I think, he is trying to evangelize "you should write readable code, no matter of the limitations of the language."
- insertnickname 10y ago
  The page does mention those.
- awjr 10y ago
  TBH it shouldn't be on the front page of HN.
realharo 10y ago
You can now use async/await directly in node (no transpiler necessary), and both Babel and TypeScript can compile them for browser use. Also there are now many more libraries that use native ES6 promises. Before: function getPhoto(callback) { someCustomHttpGet("/favorite_photo_id", function(err, data) { if (err) { return callback(err) } try { var dataJson = JSON.parse(data) someCustomHttpGet(dataJson.url, function(err, data) { if (err) { return callback(err) } callback(undefined, processData(data)) }) }catch(e) { callback(e) } }) } After: async function getPhoto() { const data = await fetch("/favorite_photo_id") const dataJson = await data.json() const photoData = await fetch(dataJson.url) return processData(photoData) } The example may be a bit contrived, but you get the idea.
- camus2 10y ago
  Your try catch is useless here, AFAIK JSON.stringify doesn't throw. and you can't catch someCustomHttpGet() "exceptions" if the latter is supposed to be asynchronous. relevant: http://journal.stuffwithstuff.com/2015/02/01/what-color-is-your-function/ http://journal.stuffwithstuff.com/2015/02/01/what-color-is-y...
  - realharo 10y ago
    Yeah, I messed it up when quickly typing the code without thinking, it should've been JSON.parse, I fixed it now. Also regarding that article: you can call async functions from non-async functions - you will simply get the Promise object instead of the data. If you're using TypeScript, your editor will immediately highlight the error if you try to use that Promise object as though it were the data, so zero chance of getting it wrong. Try it yourself - https://goo.gl/vDk3Gz https://goo.gl/vDk3Gz - hover over the `n` inside the `formatName` call.
    - camus2 10y ago
      > Also regarding that article: you can call async functions from non-async functions - you will simply get the Promise object instead of the data. async function() getZ(){ return promise } function() getX(){ return x = y * getZ() } // sync call globally. let x = getX(); // NaN async/await makes things more readable, it doesn't change the issue of leaky abstraction and you need to know whether the call is blocking or non blocking when calling getZ and using a function that calls getZ. What should you do? assume everything is asynchronous by default? Imagine you have a validation lib, you don't need it to be asynchronous to validate a string of length > 10, but you need to rewrite your whole API if you need to validate the fact a unique index has to be validated from a database.

awjr 10y ago

Promises and, more recently, Observables. Simply put: A promise resolves to a single value asynchronously, an observable resolves to (or emits) multiple values asynchronously (over time). Taken from here: http://stackoverflow.com/questions/36064303/what-are-the-differences-between-observables-and-promises-in-javascript http://stackoverflow.com/questions/36064303/what-are-the-dif...

awjr 10y ago
Oh I also forgot async/await "The purpose of async/await functions are to simplify the behavior of using promises synchronously and to perform some behavior on a group of Promises. Just like Promises are similar to structured callbacks, async/await is similar to combining generators and promises." https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...

Kiro 10y ago

Promises and async/await. This page is so outdated it shouldn't exist.

mromanuk 10y ago
He addressed more modern solutions at the bottom. I think, he is trying to evangelize "you should write readable code, no matter of the limitations of the language."
insertnickname 10y ago
The page does mention those.
awjr 10y ago
TBH it shouldn't be on the front page of HN.

realharo 10y ago

You can now use async/await directly in node (no transpiler necessary), and both Babel and TypeScript can compile them for browser use. Also there are now many more libraries that use native ES6 promises. Before: function getPhoto(callback) { someCustomHttpGet("/favorite_photo_id", function(err, data) { if (err) { return callback(err) } try { var dataJson = JSON.parse(data) someCustomHttpGet(dataJson.url, function(err, data) { if (err) { return callback(err) } callback(undefined, processData(data)) }) }catch(e) { callback(e) } }) } After: async function getPhoto() { const data = await fetch("/favorite_photo_id") const dataJson = await data.json() const photoData = await fetch(dataJson.url) return processData(photoData) } The example may be a bit contrived, but you get the idea.

camus2 10y ago
Your try catch is useless here, AFAIK JSON.stringify doesn't throw. and you can't catch someCustomHttpGet() "exceptions" if the latter is supposed to be asynchronous. relevant: http://journal.stuffwithstuff.com/2015/02/01/what-color-is-your-function/ http://journal.stuffwithstuff.com/2015/02/01/what-color-is-y...
- realharo 10y ago
  Yeah, I messed it up when quickly typing the code without thinking, it should've been JSON.parse, I fixed it now. Also regarding that article: you can call async functions from non-async functions - you will simply get the Promise object instead of the data. If you're using TypeScript, your editor will immediately highlight the error if you try to use that Promise object as though it were the data, so zero chance of getting it wrong. Try it yourself - https://goo.gl/vDk3Gz https://goo.gl/vDk3Gz - hover over the `n` inside the `formatName` call.
  - camus2 10y ago
    > Also regarding that article: you can call async functions from non-async functions - you will simply get the Promise object instead of the data. async function() getZ(){ return promise } function() getX(){ return x = y * getZ() } // sync call globally. let x = getX(); // NaN async/await makes things more readable, it doesn't change the issue of leaky abstraction and you need to know whether the call is blocking or non blocking when calling getZ and using a function that calls getZ. What should you do? assume everything is asynchronous by default? Imagine you have a validation lib, you don't need it to be asynchronous to validate a string of length > 10, but you need to rewrite your whole API if you need to validate the fact a unique index has to be validated from a database.