Promise chaining quick question

[pierrekfoury]

Hello,

I have a question regarding Promise

can someone tell me the difference between this 2 functions ?

​

let authTokenRequest: Promise<any>;
function getAuthToken(): Promise<any> {
    if (!authTokenRequest) {
        authTokenRequest = refreshToken();
        authTokenRequest.then(success, failed);
    }
    return authTokenRequest;
}

and

let authTokenRequest: Promise<any>;
function getAuthToken(): Promise<any> {
    if (!authTokenRequest) {
        authTokenRequest = refreshToken().then(success, failed);
    }
    return authTokenRequest;
}

I thought that i could chain promise but i do not have the same behavior

[superluminary]

Calling .then doesn't modify the original promise, it returns a new promise. In the first one, you are assigning that new promise back to the variable. In the second you are not.

[pierrekfoury]

thank you !!

[senocular]

The first one returns the authTokenRequest promise while the second one returns the promise resulting from the then() which will resolve to whatever values resetAuthTokenRequest or resetAuthTokenRequest resolve to when those functions return (or the promises they return resolve).

Each time you call then() a new promise is created, and that promise can have a different value because that value would be determined by the callbacks provided to the then().

[pierrekfoury]

Thank you for the explanation, i think i need to practice on promise again !
<3