multiple then in the promises usage

promises.js

/*
USE OF MUTIPLE THEN IN THE PROMISES

Actually in then we can return a sync value or 
multiple async values

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/then#Chaining
**/

var p1 = new Promise(function (resolve, reject) {
    setTimeout(function () {
        console.log("waited for 2000 ms")
        resolve('waited 2000 ms')
    }, 2000)
}).then(function (data) {
    //HERE WE CAN RETURN THE PROMISE AS  VALUE
    return new Promise(function (resolve, reject) {
        setTimeout(function () {
            console.log("waited for 3000 ms")
            resolve('waited 3000 ms')
        }, 3000)
    })
}).then(function (data) {
    //HERE ALSO DOING THE SAME
    return new Promise(function (resolve, reject) {
        setTimeout(function () {
            console.log("waited for 4000 ms", data)
            resolve('waited 4000 ms')
        }, 4000)
    })
}).then(function (data) {
    console.log("Finally????", data)
}).catch(function (err) {
    console.log("errr", err)
}).finally(function () {
    console.log("clear the values finally")
})