Promises
suggest changeSyntax
- new Promise( /* executor function: */ function(resolve, reject) { })
- promise.then(onFulfilled[, onRejected])
- promise.catch(onRejected)
- Promise.resolve(resolution)
- Promise.reject(reason)
- Promise.all(iterable)
- Promise.race(iterable)
Remarks
Promises are part of the ECMAScript 2015 specification and browser support is limited, with 88% of browsers worldwide supporting it as of July 2017.
In environments which do not support them, Promise
can be polyfilled. Third-party libraries may also provide extended functionalities, such as automated “promisification” of callback functions or additional methods like progress
—also known as notify
.
The Promises/A+ standard website provides a list of 1.0 and 1.1 compliant implementations. Promise callbacks based on the A+ standard are always executed asynchronously as microtasks in the event loop.
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