function doSomething() {
return new Promise((resolve, reject) => {
console.log("It is done.");
// Succeed half of the time.
if (Math.random() > .5) {
resolve("SUCCESS")
} else {
reject("FAILURE")
}
})
}
const promise = doSomething();
promise.then(successCallback, failureCallback);//create a Promise
var p1 = new Promise(function(resolve, reject) {
resolve("Success");
});
//Execute the body of the promise which call resolve
//So it execute then, inside then there's a throw
//that get capture by catch
p1.then(function(value) {
console.log(value); // "Success!"
throw "oh, no!";
}).catch(function(e) {
console.log(e); // "oh, no!"
});
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 */ }
);console.log('some piece of code');
examplePromise.then(function(result){
console.log(result);
}).catch(function (error) {
console.error(error);
});
console.log('another piece of code');let promise = new Promise((resolve,reject)=>{
try {
resolve("some data");
} catch (error) {
reject(error);
}
})
promise.then(function (data) {
console.log(data);
},function (error) {
console.error(error);
})A Promise is in one of these states:
pending: initial state, neither fulfilled nor rejected.
fulfilled: meaning that the operation was completed successfully.
rejected: meaning that the operation failed.