js create a promise
/*
A Promise is a proxy for a value not necessarily known when the promise is created.
It allows you to associate handlers with an asynchronous action's eventual success
value or failure reason.
*/
let promise = new Promise((resolve , reject) => {
fetch("https://myAPI")
.then((res) => {
// successfully got data
resolve(res);
})
.catch((err) => {
// an error occured
reject(err);
});
});promise
new Promise( (res, rej) => {
setTimeout(() => res(1), 1000);
}).then( (res) => {
console.log(res); // 1
return res*2
}).then( (res) => {
console.log(res); // 2
});javascript promises
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 */ }
);javascript create promise
// base case
const promise = new Promise(executor);
// more complex example
const coinflip = (bet) => new Promise((resolve, reject) => {
const hasWon = Math.random() > 0.5 ? true : false;
if (hasWon) {
setTimeout(() => {
resolve(bet * 2);
}, 2000);
} else {
reject(new Error("You lost...")); // same as -> throw new Error ("You lost ...");
}
});object promise javascript
let promise = new Promise(function(resolve, reject){
try{
resolve("works"); //if works
} catch(err){
reject(err); //doesn't work
}
}).then(alert, console.log); // if doesn't work, then console.log it, if it does, then alert "works"promise in js
myPromise
.then(handleResolvedA)
.then(handleResolvedB)
.then(handleResolvedC)
.catch(handleRejectedAny)
.finally(handleComplition)Copyright © 2021 Codeinu
Forgot your account's password or having trouble logging into your Account? Don't worry, we'll help you to get back your account. Enter your email address and we'll send you a recovery link to reset your password. If you are experiencing problems resetting your password contact us
