Is possible to call async function without await keyword? and what happens if we call without await?

Question

I would like to do the following and keep in mind it actually works for me. my question is what happens and Is possible to call async usrs() func from non async componentDidMount() func? if it is not possible why it is working for me by calling this.usrs(usrs) instead of await this.usrs(usrs);

let outState = {};
class A extends Component{
  componentDidMount(){
   this.usrs(usrs);
  }
  getData(usr){
    return db.collection('a/'+usr+'/bb').get().then(snap=>{
      for(i = snap.docs.length-1; i>=0; i--){
         outState[usr] = [...outState[usr], snap.docs[i].data()];
         if(i === 0) return outState;
      }
     return false;
    });
  }

  async usrs(usrs){

   let os = {}, data = {};

    for(i = usrs.length-1; i>=0; i--){

       os = await this.getData(usrs[i]);
       if(os){
          data = { ...data, ...os };
          if (i === 0) {
             this.setState({ ...this.state, ...data });
          }
       }

    }

  }

}

Answer 1

You only need await if the caller needs to wait for the function to be done, for instance when it needs the result of the function, or when it needs to wait for some state/data change that the function causes. If there is no such dependency, you can just 'fire and forget', by not using the await keyword.

As others mentioned, you could use .then as well, but the basic rule is the same: you do that, when you have something specific to do after the function is done. It can be omitted otherwise.

So concretely: With 'caller', I simply mean the function that calls the async function. In your case that would be componentDidMount. The options are then quite simple:

1. Keep as is. usrs() will be run in the background completely and componentDidMount will continue running until its end.
2. Use await, so componentDidMount will wait for the return of usrs().
3. Use usrs().then(), so componentDidMount can continue, but the code specified in .then() is invoked after usrs() returns, if you need to do something that has to happen after usrs() is done.