Example of a promise chain

promiseExample.ts

interface Todo {
  id: string
  name: string
  done: boolean
}

const createTodo = (name: string) => new Promise<Todo>((resolve) => {
  setTimeout(
    resolve,
    100,
    { id: String(Math.round(Math.random() * 1000)), name, done: false }
  )
})

// could return a new promise for force this to be always synchronous
const markAsDone = (todo: Todo): Todo => ({...todo, done: true })

const updateName = (name: string) => (todo: Todo) =>
  new Promise<Todo>(resolve => {
    setTimeout(resolve, 100, {...todo, name })
  })

const saveTodo = (todo: Todo) => new Promise<Todo>((resolve) => {
  setTimeout(resolve, 100, todo)
})

createTodo('Learn Cypress command API')
  .then(saveTodo)
  .then(updateName('Learn Cypress composition'))
  .then(markAsDone)
  .then(saveTodo)
  .then(console.log)
// a few hundred milliseconds later:
// {id: "200", name: "Learn Cypress composition", done: true}