I have a method called

fallbackToLocalDBfileOrLocalStorageDB

, which returns a promise and calls another method named getDBfileXHR, also returning a promise.

In the code snippet provided, I am unsure whether I need to use 'resolve()' explicitly or if resolving getDBfileXHR will automatically resolve

fallbackToLocalDBfileOrLocalStorageDB

.

Although I have commented out the then().catch() parts, I am uncertain about whether I should remove them entirely.

fallbackToLocalDBfileOrLocalStorageDB() {
        return new Promise(function (resolve, reject) {
            if (this.storageService.get('prodata') === null) { 
                if (this.connectionStatus.f() !== 'online') {
                } else {
                    this.sendErrorEmail("BL: online but falling back to local proDB", 10);
                }
                console.log('...falling back to local proBD.jsonp.');
                return this.getDBfileXHR('proDB.jsonp');
                    // .then(function () {
                    //    console.log('...falling back to local proBD.jsonp succeeded.');
                    //    resolve();
                    // })
                    // .catch(, function () {
                    //    console.log('...error, shit.');
                    //    reject();
                    // });

EDIT showing the full nested functions, with partially fixed code:

import { Injectable } from '@angular/core';
...

export class UpdateProDB {

    constructor(
        ) {
    }   


    get() {
        var debugOptionUseLocalDB = 0,
        prodata = [],
        serverAttempts = 0;     return new Promise((resolve, reject) => {
            if (debugOptionUseLocalDB) {
                return this.fallbackToLocalDBfileOrLocalStorageDB();
            }
            if (this.connectionStatus.f() === 'online') {
                console.log("Fetching DB from the server:");
                return this.getDBfileXHR(this.dbUrl(), serverAttempts)
                .then(function (data) { 
                    console.log('-normal XHR request succeeded.');

                    resolve(data);
                })
                .catch((reason)=> {
                    if (typeof serverAttempts !== "undefined") serverAttempts++;
                    console.log('on passe dans le catch, serverAttempts = ', serverAttempts)
                    if (serverAttempts < 2) {
                        return this.getDBfileXHR(this.dbUrl(), serverAttempts)
                        .then(function () { 
                            console.log('-basic XHR request succeeded.');

                        })
                        .catch(function (){
                            console.log("-basic XHR request failed, falling back to local DB file or localStorage DB...");

                        })
                    } else {
                        console.log("-basic XHR request failed, falling back to local DB file or localStorage DB...");
                        return this.fallbackToLocalDBfileOrLocalStorageDB()
                        .then((data)=>{
                            resolve(data);
                        })
                        .catch((reason)=> {
                            reject(reason);
                        });
                    }
                });
            });
    }   

    getDBfileXHR(url, serverAttempts) {
        return new Promise((resolve, reject) => {
            var request = new XMLHttpRequest();
            request.open("GET", url, true);             
            request.onload = ()=> {
                if ( (request.readyState === 4) && ( (request.status >= 200 && request.status <= 299) || request.status === 304 || request.status === 0) ) {
                    console.log('-we get response '+request.status+' from XHR in getDBfileXHR');

                    var jsonText = request.responseText.replace("callback(", "").replace(");", ""); 

                    if (jsonText === '') {
                        console.error('-error');

                        reject({
                            status: request.status,
                            statusText: request.statusText
                        });

                    } else {
                        var parsedJson;
                        try {
                            parsedJson = JSON.parse(jsonText);
                        } catch (e) {
                            resolve(request.response);
                        }
                    }
                };
                request.onerror = ()=> {
                    reject({
                        status: request.status,
                        statusText: request.statusText
                    });
                };
                console.log("sending request.send()");
                request.send();

            });
    }   


    fallbackToLocalDBfileOrLocalStorageDB() {
        return new Promise((resolve, reject) => {
            if (this.storageService.get('prodata') === null) { 
                if (this.connectionStatus.f() !== 'online') {

                } else {
                    this.sendErrorEmail("BL: online but falling back to local proDB", 10);
                }
                console.log('...falling back to local proBD.jsonp.');
                return this.getDBfileXHR('proDB.jsonp', undefined)
                .then(function (data) {
                    console.log('...falling back to local proBD.jsonp succeeded.');
                    resolve(data);
                })
                .catch((reason)=> {
                    console.log('...error, shit.');
                    reject(reason);
                });
            } else { 
                resolve();
            }
        });
    }