Singleton Pattern

Closure.js

import coursesData from './courses'
function CourseService() {
    let courses = coursesData;
    return {
        addCourse: (newCourse) => {
            courses.push(newCourse);
        },
        deleteCourse: (id) => {
            courses = courses.filter(course => course.id !== id)
        },
        findAllCourses: () => {
            return courses
        }
    }
}
export default CourseService();

Comp.jsx

import  CourseService from './Closure'
import  CourseService1 from './WrapperSingleton'


const Comp=()=>{
  
console.log(CourseService.findAllCourses())
return <div></div>
}

WrapperSingleton.js

// Using a  wrapper class
class CourseService {
    constructor(){
        this.instance = null;
        this.courses=[];
    }

    addCourse=(newCourse)=>{
        this.courses.push(newCourse);
    }

    deleteCourse=(id)=>{
        this.courses = this.courses.filter(course=>course.id !== id)
    }
}



class SingleTon{

    instance = null;

    static getInstance(){
        if (this.courseService)
            return this.courseService;
        else
            this.courseService= new CourseService();
        return this.courseService;
    }

}


export  default  SingleTon.getInstance();