crondate parser formatter and ui picker
npm i crond-picker
import { CrondPicker } from 'crond-picker'
import * as React from 'react'
import * as ReactDOM from 'react-dom'
ReactDOM.render(<CrondPicker value="* 30-59/2 * * *" onChange={crondStr => console.log(crondStr)} />, container)
Demo: https://codesandbox.io/s/stoic-sound-oq6w3?file=/src/App.js