Typescript: Convert For loop to Promise and wait to resolve all-CodePudding

ISSUE: save.emit() runs before all the iterations are completed in the below "for" loop which shows incorrect values of the addUpdate call inside loop.

I am trying to convert a for loop to promise and then wait for each of those promise to resolve so that I can emit changes and close a popup.

Below, is a test code in which I want to print "console.log("Print Before")" first for each iteration and then at the end print "console.log("Print After")" once all iterations are done.

Any help on the syntax for this is really appreciated.

  convertForLoopToPromiseAndWait(someParameterOfTypeObject) {
    for (var test of someParameterOfTypeObject) {
      var testVariable = test.setValue;
      if (testVariable) {         
          dataService.addUpdateEndpointCall();
          console.log("Print Before");    
      }
    }
    console.log("Print After");
    save.emit();
  }

      async addUpdateEndpointCall() {
        const promise1 =  this.dataService.addCall().take(1).toPromise();
        const promise2 =  this.dataService.deleteCall().take(1).toPromise();
    
        await Promise.all([promise1, promise2])
          .then(_ => this.save.emit());
      }

CodePudding user response：

Convert convertForLoopToPromiseAndWait to async method, then you can use await after for keyword and before dataService.addUpdateEndpointCall();

async convertForLoopToPromiseAndWait(someParameterOfTypeObject) {
  for await (var test of someParameterOfTypeObject) {
    var testVariable = test.setValue;
    if (testVariable) {         
      await dataService.addUpdateEndpointCall();
      console.log("Print Before");    
    }
  }
  console.log("Print After");
  await save.emit();
}

CodePudding user response：

I think that you have made a mistake here:

const promise1 = await this.dataService.addCall().take(1).toPromise();
const promise2 = await this.dataService.deleteCall().take(1).toPromise();

You await promises. The results put in the variables promise1 and promise2 will then not be promises.

Don't you mean the following?

      async addUpdateEndpointCall() {
        const promise1 = this.dataService.addCall().take(1).toPromise();
        const promise2 = this.dataService.deleteCall().take(1).toPromise();
    
        await Promise.all([promise1, promise2])
          .then(_ => this.save.emit());
      }