Demo12_async_promise_5.js

/**
 * * Resolve call-back hell problem
 * * ES using PROMISE - Static methods of PROMISE
 */

'use strict'

console.clear()

//? Static methods
//! - Promise.resolve(value): return promise resolved (finish) with value
//! - Promise.reject(reason): return promise reject (error) with value of error
//! - Promise.all(iterable of multiple promises):
//      + Input array of promises or non-promises objects (number, boolean, etc...)
//      + Return new promise object. 
//      + Wait all of promises objects in array must be completed/resolved (finish) by order or promises in array
//      + If we have one of promises to be rejected, this promise (rejected) will throw error, but others is continue
//      + So, these promises are executed parallel
//! - Promise.race(iterable of multiple promises):
//      + Input array of promises or non-promises objects (number, boolean, etc...)
//      + Return new promise object. 
//      + Wait all of promises objects in array must be completed. Return of promise which is completed first will return the result (Resolved/Rejected)
//! - Promise.allSettled(iterable of multiple promises):
//      + Input array of promises or non-promises objects (number, boolean, etc...)
//      + Return new promise object. 
//      + Wait all of promises objects in array must be completed. Return array of result of all of promises
//! - Promise.any(iterable of multiple promises): experimental (beta)

//? return or not return inside callback of then
const p_10 = new Promise((resolve, reject) => {
    resolve(100)
})

p_10.then(data1 => {
    console.log('P_10 is FIRST', data1)
    return data1 + 100
})
.then(data2 => {
    console.log('P_10 is SECOND', data2)
})
.then(data3 => {
    console.log('P_10 is THIRD', data3)         // data3 is undefine, because of inside function of data2 is not return value for data3
})
.catch(error => {
    console.log(error)
})
.finally(() => {
    console.log('DONE')
})