What it does: not clear.
How it's different: not clear.
Project name: bird?!
Modularity: Poor. one single JavaScript file with hundreds of lines :(
Duplicate effort, nothing new but more confuse.
I'm just tired of seeing shitty Promises libraries. And I'm a huge hater for those.
Here is a good one that I liked: https://github.com/puffnfresh/fantasy-promises
1. Its a promise library. It gives you a Promise class, a PromiseResolver and some tools to convert node functions to promises or to support dual promise/callback API.
2. Its super-fast and has full stack traces that go back until the beginning of the async event chain
3. I will skip this, because, uhh...
4. You didn't look hard enough. https://github.com/petkaantonov/bluebird/tree/master/src
5. Yes, promises are confusing. I'm going to write a straight-forward introduction (that uses bluebird) this weekend. But once you get past the new words and definitions, promises are actually not complicated at all. Infact, here is a short intro:
How are promises different? Instead of writing your functions to take callbacks, you write functions that return promises. Imagine that node's fs.readFile returned a promise instead of taking a callback. Then this code:
fs.readFile(file, function(err, res) {
if (err) handleError();
doStuffWith(res);
});
fs.readFile(file).then(function(res) {
doStuffWith(res);
}, function(err) {
handleError();
});
Its better that you can attach a callback later if you want. Remember, `fs.readFile(file)` returns a promise now, so you can put that in a var:
var filePromise = fs.readFile(file);
// do more stuff...
filePromise.then(function(res) { ... });
filePromise.then(function(res) { uploadData(url, res); });
filePromise.then(function(res) { saveLocal(url, res); });
Say you want to get a line from a file:
var linePromise = fs.readFile(file).then(function(data) {
return data.toString.split('\n')[line];
});
var beginsWithHelloPromise = linePromise.then(function(line) {
return /^hello/.test(line);
});
function readUploadAndSave(file, url, otherPath) {
// read the file
var filePromise = fs.readFile(file);
// upload it when done reading
var uploaded = filePromise.then(function(content) {
return uploadData(url, content);
});
// also save to another place locally
var savedLocal = filePromise.then(function(res) {
return fs.saveFile(res, otherPath)
});
// return a promise that "succeeds" when both saving and uploading succeed:
return Bluebird.join(uploaded, savedLocal);
}
readUploadAndSave(file, url, otherPath).then(function() {
console.log("Success!");
}, function(err) {
// This function will catch *ALL* errors, from the above
// operations including any exceptions thrown inside .then
console.log("Oops, it failed.", err);
});
function readUploadAndSave(file, url, otherPath) {
// read the file
return fs.readFile(file).then(
// upload and save when done reading
return Bluebird.join(uploadData(url, content),
fs.saveFile(res, otherPath));
});
}
function readUploadAndSave(file, url, otherPath) {
// read the file
var uploadedPromise = fs.readFile(file).then(
// return promise that its uploaded
return uploadData(url, content);
});
return uploadedPromise.then(function() {
// return promise that its saved.
return fs.saveFile(res, otherPath);
});
}
function readUploadAndSave(file, url, otherPath) {
// read the file
return fs.readFile(file).then(
// then upload it
return uploadData(url, content);
}).then(function() { // after its uploaded
// save it
return fs.saveFile(res, otherPath);
});
}
Thats all you need, really. The rest is just converting callback-taking functions to promise-returning functions and using the stuff above to do your control flow.
Ah, and also, you can also return values in case of an error. So for example, to write readFileOrDefault (which returns a default value if for example the file doesn't exist) you would do this:
function readFileOrDefault(file, line, defaultContent) {
return fs.readFile(file).then(function(fileContent) {
return fileContent;
}, function(err) {
return defaultContent;
});
}You already have async.waterfall and async.auto with .then and .spread chaining.
files.getLastTwoVersions(filename)
.then(function(items) {
// fetch versions in parallel
var v1 = versions.get(items.last),
v2 = versions.get(items.previous);
return [v1, v2];
})
.spread(function(v1, v2) {
// both of these are now complete.
return diffService.compare(v1.blob, v2.blob)
})
.then(function(diff) {
// voila, diff is ready.
});
// download all items, then get their names
var pNames = ids.map(function(id) {
return getItem(id).then(function(result) {
return result.name;
});
});
// wait for things to complete:
Promise.all(pNames).then(function(names) {
// we now have all the names.
});
// start with current being an "empty" already-fulfilled promise
var current = Promise.fulfilled();
var namePromises = ids.map(function(id) {
// wait for the previous download to complete, then get the next
// item, then extract its name.
current = current
.then(function() { return getItem(id); })
.then(function(item) { return item.name; });
return current;
});
Promise.all(namePromises).then(function(names) {
// use all names here.
});
var queued = [], parallel = 3;
var namePromises = ids.map(function(id) {
// How many items must be complete before fetching the next?
// The queued, minus those running in parallel, plus one of the parallel slots.
var minComplete = Math.max(0, queued.length - parallel + 1);
// when enough items are complete, queue another request
// for an item, then get the item's name.
return Promise.some(queued, minComplete)
.then(function() {
var download = getItem(id);
queued.push(download);
return download;
}).then(function(item) {
return item.name;
});
});
Promise.all(namePromises).then(function(names) {
// use all names here.
});