making modular javascript library by importing class methods without need to the whole class

Question

I'm trying to make a reusable javascript library for example books class and have createbook, checkforbook, modify book methods

I want to use it like so

import Library, {checkForBook, modifyBook} from 'books'


Library.createBook({
 name : 'firstbook',
 year: 2012
})


checkForBook('firstBook')

modifyBook('firstBook',{
  name: 'secondBook'
})

my problem right now is: how to do it without need to use new keywrod , and how to use methods wihout need to make it like Library.checkForBook and still have access to the list of books

Add your books script and the current issue that you're facing. Here is a similar question https://stackoverflow.com/questions/38308307/export-import-single-class-method-using-es6-modules — Harshana, Mar 23 '19 at 12:19
Can you post your `books` module source, please? Are you saying it contains a `class`? — Bergi, Mar 23 '19 at 12:30

score 0 · Answer 1 · answered Mar 23 '19 at 12:34

I think you are looking for

// library.js
export default class Library {
    …
}

// books.js
import Library from './library';

// creates a singleton:
export default const books = new Library();

export function checkForBook(name) {
    return books.checkForBook(name);
}
export function modifyBook(name, value) {
    return books.modifyBook(name, value);
}

// main.js
// imports the singleton, not the `Library` class
import books, {checkForBook, modifyBook} from 'books';

books.createBook({
 name : 'firstbook',
 year: 2012
});

checkForBook('firstBook');

modifyBook('firstBook', {
  name: 'secondBook'
});

score 0 · Accepted Answer · answered Mar 23 '19 at 12:36

  const books = new Map(); // store the books somehow

  export function createBook({ name, year }) { // make them available as import { createBook } from ...
    const book = { name, year };
    books.set(name, book);
    return book;
  }

  export function checkForBook(name) {
    return books.has(name);
  }

  export function modifyBook(name, update) {
    if(!checkForBook(name))
      throw new Error("Cannot modify, book doesnt exist");
    Object.assign(books.get(name), update);
  }

  export default { // make them available as Library.createBook
    createBook,
    checkForBook,
    modifyBook
  };

making modular javascript library by importing class methods without need to the whole class

2 Answers2