如何用 observable 重构 function

Question

How can I refactor this part of code? I want to reduce the amount of 'else if' statements. I tried to use || operator, but it's doesn't work.

getNominieesByStage(stage_key: string): Observable<any> {

    const simpleObservable$ = new Observable<any>((observer) => {

      if (stage_key === 'key1') {
        observer.next(NOMINIEES[`${stage_key}`]);
      } else if (stage_key === 'key2') {
        observer.next(NOMINIEES[`${stage_key}`]);
      } else if (stage_key === 'key3') {
        observer.next(NOMINIEES[`${stage_key}`]);
      } else if (stage_key === 'key4') {
        observer.next(NOMINIEES[`${stage_key}`]);
      } else if (stage_key === 'key5') {
        observer.next(NOMINIEES[`${stage_key}`]);
      } else if (stage_key === 'key6') {
        observer.next(NOMINIEES[`${stage_key}`]);
      } else {
        observer.next([NOMINIEES[`${stage_key}`]]);
      }

      // observable execution

      observer.complete();
    });

    return simpleObservable$;
  }

Answer 1

Your code is currently functionaly equivalent to:

 const simpleObservable$ = new Observable<any>((observer) => {
   observer.next(NOMINIEES[`${stage_key}`]);
   observer.complete();
 }
 return observer;

Without any if statement.

Also, this can be simplified further by static Observable creation methods:

return Rx.Observable.of(NOMINIEES[`${stage_key}`]);

Answer 2

create an array of keys and return values then use find

var v = someKeyValueTypeArray.find(x=>x == 'key1').someReturnValue;
observer.next(v);
observer.complete();

Answer 3

use instead of connected if-statements a switch case -element:

switch(stage_key) { 
   case 'key1','key2','key3': { 
       observer.next(NOMINIEES[`${stage_key}`]);
      break; 
   } 
   default: { 
      //statements; 
      break; 
   } 
} 

Answer 4

You could test for a regular expression like

if(/^key[1-6]/.test(stage_key)) {
   observer.next(NOMINIEES[`${stage_key}`]);
}