JAVASCRIPT

new promise function

const myPromise = new Promise((resolve, reject) => {
  setTimeout(() => {
    resolve('foo');
  }, 300);
});

myPromise
  .then(handleResolvedA, handleRejectedA)
  .then(handleResolvedB, handleRejectedB)
  .then(handleResolvedC, handleRejectedC);

javascript promise example basic

const anotherPromise = new Promise((resolve, reject) => {
  setTimeout(() => {
    resolve('this is the eventual value the promise will return');
  }, 300);
});

// CONTINUATION
anotherPromise
.then(value => { console.log(value) })

javascript Program with a Promise

const count = true;

let countValue = new Promise(function (resolve, reject) {
    if (count) {
        resolve("There is a count value.");
    } else {
        reject("There is no count value");
    }
});

console.log(countValue);

Create A Promise In JavaScript

async function abc() 
{ 	
	const myPromise = new Promise(function(resolve, reject) {
   resolve("hello world");
});
let y= await myPromise;
console.log(y);
/*"hello world*/
	}

promise syntax for javascript

let myPromise = new Promise(function(myResolve, myReject) {
// "Producing Code" (May take some time)

  myResolve(); // when successful
  myReject();  // when error
});

// "Consuming Code" (Must wait for a fulfilled Promise)
myPromise.then(
  function(value) { /* code if successful */ },
  function(error) { /* code if some error */ }
);

javascript Create a Promise

let promise = new Promise(function(resolve, reject){
     //do something
});

promise syntax in js

// make new promise ... so this object will promise us that it will hold an Asynchronous action
// some times promise resolve and some times promise get rejected
const A = new Promise((resolve, reject) => {
    setTimeout(() => {
        // here we pass argument if promise get resolved
        resolve('Done');

        // here we pass argument if promise get rejected
        reject('Didn"t');
    }, 3000);
});


// design handling callback function for resolve 
let handleResolvedA = (massage)=>{console.log(massage)}

// design handling callback function for reject 
let handleRejectedA = (massage)=>{console.log(massage)}


// do handling for both
A.then(handleResolvedA, handleRejectedA)

simple promise

getSomethingWithPromise()
  .then(data => {/* do something with data */})
  .catch(err => {/* handle the error */})

Simplest Promise Example

let hw = await new Promise((resolve)=>{
resolve(“HELLO WORLD”);

})

console.log(hw);
 
/*basically in resolve(whatever') the whatever is returned*/
/*hw will console.log out "HELLO WORLD" */

making promises in js

getData()
    .then(data => console.log(data))
    .catch(error => console.log(error));

simple promise

// jeffBuysCake is a promise
const promise = jeffBuysCake('black forest')

javascript promise example

/* Testing Grepper

js promise example

function examplePromise(){
  let promiseToReturn = new Promise(function (resolve, reject) {
    let sum;
    setTimeout(function(){
      sum = 5 + 6;
      if(sum > 10) {
        resolve(sum);
      }else{
        reject('The promise has been rejected');
      }     
    }, 2000);
  });
  return promiseToReturn;
}

console.log('some piece of code');
examplePromise().then(function(result){
  console.log(result);
}).catch(function(error){
  console.log(error);
});
console.log('another piece of code');

JavaScript Promise Methods

Method	Description
all(iterable)	Waits for all promises to be resolved or any one to be rejected
allSettled(iterable)	Waits until all promises are either resolved or rejected
any(iterable)	Returns the promise value as soon as any one of the promises is fulfilled
race(iterable)	Wait until any of the promises is resolved or rejected
reject(reason)	Returns a new Promise object that is rejected for the given reason
resolve(value)	Returns a new Promise object that is resolved with the given value
catch()	Appends the rejection handler callback
then()	Appends the resolved handler callback
finally()	Appends a handler to the promise