class.js

class Foo {
  constructor(value) {
    this.item = value
  }

  getItem() {
    return this.item
  }

  setItem(value) {
    this.item = value
  }
}

const foo = new Foo('bar')
console.log(foo.item)

foo.setItem('qux')

const item = foo.getItem()
console.log(item)