Unable to understand function parameter signature for the getMovies function of moviesDAO.js. Can anyone please simplify the parameter passed to this function

MongoDB University M220JS: MongoDB for Javascript Developers
#1 
static async getMovies({
    // here's where the default parameters are set for the getMovies method

    filters = null,

    page = 0,

     moviesPerPage = 20,

     } = {}) {

         let queryParams = {}
        .
        .
        .
}
#2

My guess is that getMovies() has 1 optional parameter. Which is an object with 3 fields. Each field having a different value. So calling getMovies() without any parameter would me get me the first 20 unfiltered movies of page 0. See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Default_parameters

1 Like
#3

Thanks for the reply. But why an empty object is assigned to the default parameter?

#4

If not you could not call getMovies() like this, without any parameter. With the given signature you can call getMovies in the following ways:

  1. getMovies() which is equivalent to getMovies({}) which is equivalent to getMovies( { filters : null, page : 0, moviesPerPage : 20 } )
  2. getMovies( { page : 2 } ) which is equivalent to getMovies( { filters : null, page : 2, moviesPerPage : 20 } )
  3. getMovies( { moviesPerPage : 16 } ) which is equivalent to getMovies( { filters : null, page : 0, moviesPerPage : 16 } )
  4. getMovies( { page : 2 , moviesPerPage : 16 } ) which is equivalent to getMovies( { filters : null, page : 2, moviesPerPage : 16 } )
  5. and many more

I am sure you get the pattern. This is standard default parameters usage.

1 Like
#5

Thanks, @steevej for the explanation. So if I am getting this right, it means to call getMovies() method without or any number of arguments we are assigning an empty object in the parameter signature.

#6

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