Why do call the methods differently? sometimes with '()' and sometimes without '()'?

Question

Scenario 1:

below method is from services.ts:

onChange(){
    if(this.initcount == null){
        this.likescount = null;
    } else {
      this.likescount = this.initcount;
    } 
}

when using it in component.ts:

  constructor(service: LikesService) {  
    this.getchange = service.onChange; ------------------> without '()'?
  }

Scenario 2: below method is from services.ts:

getArray(){
            return this.courseArray;
}

when using it in component:

constructor(service: CoursesService) {
      this.courses = service.getArray();  --------------------> with '()' ???
  }

Actually, should be dupe of [In JavaScript, does it make a difference if I call a function with parentheses?](https://stackoverflow.com/q/3246928/215552). TypeScript is a superset of JavaScript and does not differ in this respect. — Heretic Monkey, Jan 08 '20 at 22:43
If you aren't using parentheses, you aren't "calling" the method. — Sean Bright, Jan 08 '20 at 22:43

V Maharajh · Answer 1 · 2020-01-08T22:46:54.240

1

this.getchange = service.onChange;

☝️ This isn't calling onChange. It is setting getchange to be the onChange function. Somewhere else in the code, you can then use getchange to indirectly execute the code in onChange by doing getchange ().

edited Jan 08 '20 at 22:46

answered Jan 08 '20 at 22:44

V Maharajh

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That's not the line the OP is asking about. See the comments with the long arrows. Also, see the duplicate. Feel free to vote to close as a duplicate instead of answering too... – Heretic Monkey Jan 08 '20 at 22:45
Copy paste error. Thanks. Fixed. – V Maharajh Jan 08 '20 at 22:47

Why do call the methods differently? sometimes with '()' and sometimes without '()'?

1 Answers1