| Task | Promise & comments |
|---|---|
Task.create(computation) |
new Promise(computation) |
Task.of(x) |
Promise.resolve(x)With Promises behaviour is different if x is a Promise (this makes writing generic code more difficult with Promises). |
Task.rejected(x) |
Promise.reject(x) |
task.map(fn) |
promise.then(fn)With Promises behaviour is different if fn returns a Promise. |
task.chain(fn) |
promise.then(fn) |
task.mapRejected(fn) |
promise.then(undefined, fn)With Promises behaviour is different if fn returns a Promise. |
task.orElse(fn) |
promise.then(undefined, fn) |
task.ap(otherTask) |
promise.then(fn => otherPromise.then(fn))This method exists mainly for compliance with Fantasy Land Specification. With Promises behaviour is different if fn returns a Promise. |
Task.empty() |
new Promise(() => {}) |
task.concat(otherTask) |
Promise.race([promose, otherPromise])Also mainly for Fantasy Land, makes Task a Monoid. |
Task.parallel(tasks) |
Promise.all(promises) |
Task.race(tasks) |
Promise.race(promises) |
Task.run({success, failure}) |
Promise.then(successOrFailure) In Promises second callback is for exceptions. More about it here. |
Task.run({success, failure, catch}) |
Promise.then(successOrFailure, catch)By default tasks don't catch exceptions thrown from map, chain etc. But we can choose to catch them by providing catch callback. Also notice that exceptions go into their own callback. |
cancel = task.run(...); cancel() |
Promises don't support cancelation or even unsubscribing. |