Is there a way to wait until a function is finished?

Question

I\'m trying to get information (true/false) from AsyncStorage in a function and create a string which is importent to fetch data in the next step. My problem is, the function is

Answer 1

what if you wrap the _getFetchData() in a Promise? This would enable you to use

var channel = this._getFetchData().then(console.log("channel required: " + channel));

Otherwise the console.log won't wait for the execution of the _getFetchData(). This is what the console.log is telling you. it just logs the string. the variable is added after the async operation is done.

UPDATE

I would try this:

//_getFetchData()
AsyncStorage.getAllKeys().then((result) => { //get all stored Keys
  valuelength = result.length;
  if (valuelength !== 0) {
    for (let i = 0; i < valuelength; i++) {
      if (result[i].includes("not") == false) { //get Keys without not
        AsyncStorage.getItem(result[i]).then((resultvalue) => {
          if (resultvalue === 'true') {
            if (this.state.firstValue) {
              this.state.channels = this.state.channels + "channel_id" + result[i];
              console.log("channel: " + this.state.channels);
            }
            else {
              this.state.channels = this.state.channels + "channel" + result[i];
            }
          }
        });
      }
return new Promise((resolve, reject) => {
    this.state.channels !=== undefined ? resolve(this.state.channels) : reject(Error('error '));
}

_fetchData() {
var channel = this._getFetchData().then(console.log("channel required: " + channel));
}

maybe you must change the this.state.channels !=== undefined to an expression that's matches the default value of this.state.channels.