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 */ }
);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 javascript
/*
Promise is a constructor function, so you need to use the new keyword to
create one. It takes a function, as its argument, with two parameters -
resolve and reject. These are methods used to determine the outcome of the
promise.
The syntax looks like this:
*/
const myPromise = new Promise((resolve, reject) => {
});promise javascript
const promiseA = new Promise( (resolutionFunc,rejectionFunc) => {
resolutionFunc(777);
});
// At this point, "promiseA" is already settled.
promiseA.then( (val) => console.log("asynchronous logging has val:",val) );
console.log("immediate logging");
// produces output in this order:
// immediate logging
// asynchronous logging has val: 777js promise
const prom = new Promise((resolve, reject) => {
resolve('Yay!');
});
const handleSuccess = (resolvedValue) => {
console.log(resolvedValue);
};
prom.then(handleSuccess); // Prints: 'Yay!'Copyright © 2021 Codeinu
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