Function returns undefined instead of result of the request

Question

I have some problems with the asynchronous in javascript. There is a function(next) that repeatedly sending REST API requests to a server. The functions will call itself until the root ID is found. You can find console.log('the root ID is reached!') at the spot. After that, I need the last request ID as the returned result of the function(next) but instead, it returns "undefined".((

function next(initId) {
       return requestHttp('GET','https://www.wrike.com/api/v4/folders/' + initId)
        .then(function(response: string) {
            let folderObj =  JSON.parse(response);
            initId = folderObj.data[0].parentIds;
            if (folderObj.data[0].parentIds === WebHook.rootId) {
               console.log('the root ID is reached!');
               return folderObj.data[0].id;
            } else {
                next(initId); 
            }   
        }, function(error) {
            return error;
        });      
}

next(obj.data[0].parentIds).then(function(response) {
    console.log(response);
}).catch(function(err) {
    console.log(err);
});

Lines 8, 10 and 13 must return a resolved or rejected Promise in order to use .then() on next() method — Stephane Janicaud, Mar 18 '20 at 17:07

Stephane Janicaud · Accepted Answer · 2020-03-18T20:09:43.833

1

According to Wrike.com api, you don't have to do this to find the root folder id. https://developers.wrike.com/documentation/api/methods/get-folder

[GET] /folders/{folderId} returns a parentIds property which is an array of parent folders ids.

I don't have an account but I'm quite sure that either the first or the last one in this array (depending on the order) is the ROOT folder id you wan't to find.

Edit

I'm not really sure what you're trying to do but in the meantime, there are several essential errors to fix in your code :

First, here is the right way to return a chained promise

function next(initId) {
    let promise = new Promise(function(resolve, reject) {
    requestHttp('GET','https://www.wrike.com/api/v4/folders/' + initId)
        .then(function(response) {
            if(/*condition to resolve promise*/) {
                resolve(/*with something*/);
            }
            else {
                reject(/*with an error*/);
                // or return another Promise
            }
        })
        .catch(error => reject(error));
    });
    return promise;            
}

Then, the next method takes a parameter called initId so another developer (like us) does not think it's an array of ids.

I mean, it's quite confusing. It works because the parentIds property is an array and the .toString() of this array returns id1,id2,...

Wrike api supports it but you should use ids.join(',') instead.

edited Mar 18 '20 at 20:09

answered Mar 18 '20 at 17:15

Stephane Janicaud

3,531
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Sorry, but it's not the question of the ROOT or Wrike.com api. I'm just trying to find the way how to get the value that I need – Volodymyr M. Yovchenko Mar 18 '20 at 17:25
Check my comment on your answer. You don't return a Promise but values, that's why it does not work. – Stephane Janicaud Mar 18 '20 at 17:45
Checkout my updated answer to understand how to return chained promise – Stephane Janicaud Mar 18 '20 at 20:10
Thank you, I appreciate your help. You give me a hint. My main task is to find an array of custom fields and inherit them for child elements. For that, I need to loop through parent objects. – Volodymyr M. Yovchenko Mar 19 '20 at 08:12
by the way, you are right about parentIds. it is an array – Volodymyr M. Yovchenko Mar 19 '20 at 08:56
I think you don't have to call `next()` method recursively. Call `/api/v4/folders/$id` once then if you have 3 parentIds for this folder, make 3 calls and for each result, concat the custom fields. That should do the job. – Stephane Janicaud Mar 19 '20 at 09:06

score 0 · Answer 2 · answered Mar 18 '20 at 17:02

0

Try return Promise.resolve(initId) instead of next(initId).

answered Mar 18 '20 at 17:02

Eggon

2,032
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in the case, the function returns initial ID but not the last one – Volodymyr M. Yovchenko Mar 18 '20 at 17:07
Sorry, yes you should return `Promise.resolve(folderObj.data[0].id)` instead of `return folderObj.data[0].id;`. But how do you iterate through the ids if you always reference element 0 in the array? – Eggon Mar 18 '20 at 17:13
initId = folderObj.data[0].parentIds - the following line of code moves up to the next ID at every iteration – Volodymyr M. Yovchenko Mar 18 '20 at 17:18
The problem is that the function returns result after initialization – Volodymyr M. Yovchenko Mar 18 '20 at 17:42

Volodymyr M. Yovchenko · Answer 3 · 2020-03-19T08:55:13.723

function next(initId, taskId) {
    let promise = new Promise(function(resolve, reject) {
     (async function nextRequest (){   
     await requestHttp('GET','https://www.wrike.com/api/v4/folders/' + initId)
            .then(function(response: any) {
                let folderObj = JSON.parse(response);
                initId = folderObj.data[0].parentIds[0];
                if (initId == WebHook.rootId) {
                    resolve('resolve');
                }
                else {
                    nextRequest();
                }
            })
            .catch(error => reject(error));
        }());
    });
    return promise;            
}

next(obj.data[0].parentIds, true).then(function(response) {
    console.log(response);
}).catch(function(err) {
    console.log(err);
});

the answer to the question

Function returns undefined instead of result of the request

3 Answers3