promises ES6 probleme

Question

hi everyone, how do you doing
Please I have some issues here when I exec the code below can someone tell me what is wrong !!! ? I just try to learn promises in ES6
the result of this code is undefined and I don't know why

let variable = true;
function Calculate(Number1, Number2){
return new Promise(function(resolve, reject){
setTimeout(function(){
const some = Number1 + Number2;
if(variable){
resolve(some);
} else {
reject('Sorry');
}
}, 1500)
})
}
function promptAlert(number){
return new Promise(function(resolve, reject){
setTimeout(function(){
number += 2;
resolve(number);
}, 1000);
})
}

Calculate(5,5)
.then((some) => {
promptAlert(some);
})
.then((num) => {
alert(num);
})

Answer 1

return promptAlert ,otherwise it will operate on the previous promise object.

Answer 2

Instead of using an anonymous function as a call back, you can use promptAlert as the callback. The same is also true for the second then, alert can be the callback

.then(promptAlert).then(alert)

Answer 3

thank you so much for your help :)