var promise = new Promise(function(resolve, reject) {
// do some long running async thing…
if (/* everything turned out fine */) {
resolve("Stuff worked!");
}
else {
reject(Error("It broke"));
}
});
//usage
promise.then(
function(result) { /* handle a successful result */ },
function(error) { /* handle an error */ }
);const promise1 = new Promise((resolve, reject) => {
setTimeout(() => {
resolve('foo');
}, 300);
});
promise1.then((value) => {
console.log(value);
// expected output: "foo"
});
console.log(promise1);
// expected output: [object Promise]Promises make async javascript easier as they are easy to use and write than callbacks. Basically , promise is just an object , that gives us either success of async opertion or failue of async operationsmyPromise
.then(handleResolvedA)
.then(handleResolvedB)
.then(handleResolvedC)
.catch(handleRejectedAny)
.finally(handleComplition)