Promises are usefull objects, that can be used for asyncronous tasks and callbacks.
Promises return a values even if the underyling functionality fails
Use cases
- escape 'callback hell'
- react to returned data (when it returns)
Creating & Resolving Promises
Promises expect two paramaters
- resolve : {paramater} function() resolve - executed if the promise is fulfileld sucessfully
- reject : {paramater} function() reject - executed if the promise fails
Example - Basic Promise : Resolve
//Promises in ES6 - Basic Setup - Resolving Promises
let promise = new Promise(function(resolve, reject) {
setTimeout(function() {
resolve('Promise Resolved!');
}, 1500);
});
promise.then(function(value) {
console.log(value);
});
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Rejecting Promises
Example - Basic Promise : Reject
//Promises in ES6 - Basic Setup - Reject Promises
let promise = new Promise(function(resolve, reject) {
setTimeout(function() {
reject('Promise Rejected!');
}, 1500);
});
promise.then(function(value) {
console.log(value);
}, function(error) {
console.log(error);
});
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