To set promiseChain or not to set promiseChain, that is the question

promise-if-example-01.js

const printablePromise = text =>
    new Promise(resolve => {
        console.log(text)
        return resolve()
    })

const actionA = () => printablePromise('A')
const actionB = () => printablePromise('B')
const actionC = () => printablePromise('C')
const actionD = () => printablePromise('D')
const endAction = () => printablePromise('Done !')

const flag = true

let promiseChain

if (flag) {
    promiseChain = actionA().then(actionB)
} else {
    promiseChain = actionC()
}

promiseChain
    .then(actionD)
    .then(endAction)

/*
Excepted print:

A
B
D
Done !

Prints:

A
B
D
Done !
*/

promise-if-example-02.js

const printablePromise = text =>
    new Promise(resolve => {
        console.log(text)
        return resolve()
    })

const actionA = () => printablePromise('A')
const actionB = () => printablePromise('B')
const actionC = () => printablePromise('C')
const actionD = () => printablePromise('D')
const endAction = () => printablePromise('Done !')

const flag = true

let promiseChain = actionC()

if (flag) {
    promiseChain = actionA().then(actionB)
}

promiseChain
    .then(actionD)
    .then(endAction)

/*
Excepted print:

A
B
D
Done !

Prints:

C
A
B
D
Done !
*/