CODEWITHSUNDEEP
javascriptpromisees6-promise
Fiat Pax
Fiat Pax

Reputation: 417

Javascript - Promises stay as pending

Why do my promises stay in the pending state and how do I fix it?

    var foundPeopleA = findPeopleA().then(function(result) {
        var res = []
        result.map(function(el) {
            res.push(getProfileXML(el.sid));
        });
        return res
    });

    var foundPeopleB = findPeopleB().then(function(result) {
        var res = []
        result.map(function(el) {
            res.push(getProfileXML(el.sid));
        });
        return res
    })

    return Promise.all([findPeopleA, findPeopleB]).then(function(results) {
        console.log(results) //[ [ Promise { <pending> }, Promise { <pending> } ],  [ Promise { <pending> }, Promise { <pending> } ] ]
    })

However if i change the body of the 2 functions above into 

        var res
        result.map(function(el) {
            res = getProfileXML(el.sid);
        });
        return res

they won't be pending and I'll get the result.

Upvotes: 0

Views: 1456

Answers (3)

user1715408
user1715408

Reputation:

The problem is that you are handling the promises fulfillment on each of them individually by using then, and all handles the fulfillment of multiple promises by passing it an array of unresolved promises. It builds a new promise with the results of all of them together. Just use:

Promise.all([findPeopleA(), findPeopleB()])
.then(function(responses) ...

Upvotes: 1

Aaron Franco
Aaron Franco

Reputation: 1580

Try assigning your Array to the result of the mapping.

var foundPeopleA = findPeopleA().then(function(result) {
    var res = []
    res = result.map(function(el) {
        return getProfileXML(el.sid);
    });
    return res
});

Or, perhaps you can resolve the promise?

var foundPeopleA = findPeopleA().then(function(result) {
    var res = []
    res = result.map(function(el) {
        return getProfileXML(el.sid);
    });
    resolve(res);
});

Either way, I belive you need to build your array by returning values from the mapping to create the new array.

Upvotes: 0

Amadan
Amadan

Reputation: 198324

Arrays are not promises. If you return an array of promises, then gets an array of promises - just like if you return any other non-promise value. Only if you return a promise, the promise will get executed before then. Your foundPeopleA and foundPeopleB each construct an array of promises; you need to concatenate those arrays and pass them to Promise.all or equivalent in order to get them executed.

Upvotes: 1

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