React Native: synchronously run functions
<p>I'm new to OOP. My knowledge of promises/asynchronously/synchronously running functions is simply basic. I'd really appreciate your time and attention!</p>

<p>This is the example from React-Native docs:</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>async function getMoviesFromApi() {
    try {
      let response = await fetch('https://facebook.github.io/react-native/movies.json');
      let responseJson = await response.json();
      return responseJson.movies;
    } catch(error) {
      console.error(error);
    }
  }</code></pre>
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</p>

<p>As i understand from code above, getMoviesFromApi is declared as async function. which means it will execute functions one after other. Right? please correct me if not!</p>

<p>it will first wait for fetch to finish then call response.json, right?</p>

<p>I have few functions, which get data from a server via fetch, then insert them to sqlite database. so they don't return anything.</p>

<p>in example above, fetch returns something. but my functions, not. so, can i use this structure to make javascript run my functions consequently? what is the best practice / right solution to achieve this?</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>let query = [];
export default class Main extends Component(){
  constructor(props){
    super(props);
  }
  
  componentWillMount(){
    this.getBookable();
    this.getBooked();
    this.runQuery();
    this.redirectUser();
    //// i need this functions to run consequently. not all in same time, one after eachother
  }
  
  getBookable(){
    let fetchedData = fetch(); /// Fetchs data from remote server
    query.push('INSERT INTO bookable (data) VALUES (' + fetchedData + ')');
  }
  
  getBooked(){
    let fetchedData = fetch(); /// Fetchs data from remote server
    query.push('INSERT INTO booked (data) VALUES (' + fetchedData + ')');
  }
  
  runQuery(){
    for(let i=0; i &lt; query.length; i++){
      db.transaction((tx) =&gt; {
        tx.executeSql(query[i],[], (tx, results) =&gt; {
            console.log('Query', query[f], 'Executed. results:', results);
        }, (err)=&gt;{
            console.log('Something went wrong while executing query',query[i],'error is', err);
          });
      });
    }
  }
  
  redirectUser(){
    Actions.tabbar({type: 'reset'});
    //// Using redux. redirect user to another page
  }
  
}</code></pre>
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First, i get bookable courses, then booked courses, insert them to database, then redirect user to another page via redux
How should i update my code?</p>

<hr>

<p>UPDATE :</p>

<p>updated code according to @Bergi :
is this the right way?</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>import React, {Component, PropTypes} from 'react';
import {
  ActivityIndicator,
  StyleSheet,
  Text,
  View,
  NetInfo,
  AlertIOS,
} from 'react-native';

var SQLite = require('react-native-sqlite-storage');
var Loading = require("./Loading");
var DeviceInfo = require('react-native-device-info');
import { Actions } from 'react-native-router-flux';
var LOADING = {};
var db = SQLite.openDatabase({name : "oc.db", location: 'default'});
import CodePush from "react-native-code-push";
import I18n from 'react-native-i18n';
import translations from './translations';
I18n.fallbacks = true;

export default class Grab extends Component{
  constructor(props) {
        super(props);
        this.state = {
            terms: '',
            isLoading: false,
            isConnected: null,
            coursesFetched: false,
            registerFetched: false,
        };
    }

  componentWillMount() {

    NetInfo.isConnected.fetch().then(isConnected =&gt; {
      this.setState({
        isConnected: isConnected
      });
    });

    NetInfo.isConnected.addEventListener(
      'change',
      isConnected =&gt; {
        this.setState({
          isConnected: isConnected
        });
        console.log('Grab: internet status is', this.state.isConnected);
        this.sync();
      }
    );

    this.GrabData();

  }

  toggleAllowRestart() {
    this.state.restartAllowed
      ? CodePush.disallowRestart()
      : CodePush.allowRestart();

    this.setState({ restartAllowed: !this.state.restartAllowed });
  }

  sync() {
    console.log("Grab: Running manual code push update");
  CodePush.sync(
    {
      installMode: CodePush.InstallMode.IMMEDIATE,
      updateDialog: false
    },
  );
}

  async getUsers(){
    let userlist = [];
    let query = ["SELECT * FROM users"];
    await db.transaction(tx =&gt; {
      return Promise.all(query.map(async (q) =&gt; {
        try {
          let results = await tx.executeSql(q, []);
          console.log('Query', q, 'Executed. results:', results);
          for(let ind = 0; ind &lt; len; ind++ ){
            userlist[ind] = {
              userId: results.rows.item(ind).userId,
              userName: results.rows.item(ind).userName,
              userMail: results.rows.item(ind).userMail,
              active: results.rows.item(ind).active,
              firstName: results.rows.item(ind).firstName,
              lastName: results.rows.item(ind).lastName,
              accessToken: results.rows.item(ind).access_token,
              host: results.rows.item(ind).host,
            };
          }
        } catch(err) {
          console.log('Something went wrong while executing query', q, 'error is', err);
        }
      }));
    });
    return userlist;
  }

  async getBookable(users){
    let results = [];
    for(let n=0; n &lt; users.length; n++){
      try {
        let host = users[n].host;
        let access_token = users[n].access_token;
        let userId = users[n].userId;
        let response = await fetch(host + 'event/my_events', {
          method: 'POST',
          headers: {
            'Accept': 'application/json',
            'Content-Type': 'application/json',
            'language': DeviceInfo.getDeviceLocale(),
            'Authorization': 'Bearer ' + access_token
          }
        });
        let responseData = await response.json();
        //// Get container details
        if(responseData.container.length &gt; 0){
          for(let i=0; i &lt; responseData.container.length; i++){
            let cnid = responseData.container[i].nid;
            let ctitle = responseData.container[i].title;
            results.push(
              "INSERT INTO containersC (userId, nid, title) VALUES ('" + userId + "','" + cnid + "', '" + ctitle + "')"
            );
            //// Get courses for each container
            for(let j=0; j &lt; responseData.container[i].course.length; j++){
              let course_id = responseData.container[i].course[j].nid;
              let title = responseData.container[i].course[j].title;
              let cost = responseData.container[i].course[j].cost;
              let status = responseData.container[i].course[j].status;
              let period = responseData.container[i].course[j].period.time_sys;
              //// Get details for each course
              try {
                let resp = await fetch(host + 'event/course_detail/' + course_id, {
                  method: 'POST',
                  headers: {
                    'Accept': 'application/json',
                    'Content-Type': 'application/json',
                    'language': DeviceInfo.getDeviceLocale(),
                    'Authorization': 'Bearer ' + access_token
                  }
                });
                let respData = await resp.json();

                let desc = respData.data.content[0].value;
                let capacity = respData.data.content[1].value;
                let image = respData.data.image;
                let status = respData.data.book;
                let cancel = respData.data.cancel;
                let cd = responseData.data.dates;

                results.push(
                  "INSERT INTO courses (userId, course_id, container_nid, title, cost, status, period, desc, capacity, image, cancel) VALUES ('" + userId + "','" + course_id + "', '" + cnid + "', '" + title + "', '" + cost + "', '" + status + "', '" + period + "', '" + desc + "', '" + capacity + "', '" + image + "', '" + cancel + "')"
                );

                //// Getting lecture dates for each course
                for(let a=0; a &lt; cd.length; a++){
                  let sdate = cd[a].start_time.split(" ");
                  let edate = cd[a].end_time.split(" ");
                  results.push(
                    "INSERT INTO lectures (userId, course_id, title, start_time, end_time, start_date, end_date, room, teacher) VALUES ('" + userId + "','" + course_id + "', '" + cd[a].title + "', '" + sdate[1] + "', '" + edate[1] + "', '" + sdate[0] + "', '" + edate[0] + "', '" + cd[a].room + "', '" + cd[a].teacher + "')"
                  );
                }
                //// End getting lecture dates for courses
                return true;
              } catch(error) {
                console.error(error);
              }
              //// End getting details for courses
            }
            //// End getting courses for containers
          }
        }
        //// End getting container details
        return true;
      } catch(error) {
        console.error(error);
      }
    }
  }

  redirectUser(){
    Actions.tabbar({type: 'reset'});
  }

  async runQuery(query) {
    await db.transaction(tx =&gt; {
      return Promise.all(query.map(async (q) =&gt; {
        try {
          let results = await tx.executeSql(q, []);
          console.log('Query', q, 'Executed. results:', results);
        } catch(err) {
          console.log('Something went wrong while executing query', q, 'error is', err);
        }
      }));
    });
    return true;

  }

  async function GrabData(){
    try {
      let users = await getUsers();
      //let [courses, register, evaluation] = await Promise.all([getCourses(users), getRegister(users), getEvaluation(users)]);
      let [courses] = await Promise.all([getCourses(users)]);
      //let query = [courses, register, evaluation];
      let query = [courses];
      await runQuery(["DELETE FROM containersC", "DELETE FROM courses", "DELETE FROM lectures", "DELETE FROM containersR", "DELETE FROM register", "DELETE FROM lectures", "DELETE FROM evaluations", "DELETE FROM fields"]);
      await runQuery(query);
      this.redirectUser();
    } catch(error){
      console.log(error);
    }
  }


  render() {

return(
    &lt;View style={styles.container}&gt;&lt;Loading/&gt;&lt;/View&gt;
  );
  }

}

var styles = StyleSheet.create({
    container: {
      flex: 1,
      backgroundColor: "#fff",
      flexDirection: "column",
    },
});

Grab = CodePush(Grab);</code></pre>
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</p>

<p>I'm using react-native-sqlite-storage :
<a href="https://github.com/andpor/react-native-sqlite-storage" rel="nofollow">https://github.com/andpor/react-native-sqlite-storage</a></p>