combining-the-command-pattern-with-state-pattern-in-java-script_1.js

let state = { backgroundColor: 'white', profiles: [] }
let subscribers = []

function notifySubscribers(...args) {
  subscribers.forEach((fn) => fn(...args))
}

function setBackgroundColor(color) {
  setState((prevState) => ({
    ...prevState,
    backgroundColor: color,
  }))
}

function setState(newState) {
  let prevState = state
  state =
    typeof newState === 'function'
      ? newState(prevState)
      : { ...prevState, ...newState }

  notifySubscribers(prevState, state)
}

function subscribe(callback) {
  subscribers.push(callback)
}

function addProfile(profile) {
  setState((prevState) => ({
    ...prevState,
    profiles: prevState.profiles.concat(profile),
  }))
}

subscribe(
  (function () {
    function getColor(length) {
      if (length >= 5 && length <= 8) return 'blue' // Average
      if (length > 8 && length < 10) return 'orange' // Reaching limit
      if (length > 10) return 'red' // Limit reached
      return 'white' // Default
    }

    return (prevState, newState) => {
      const prevProfiles = prevState?.profiles || []
      const newProfiles = newState?.profiles || []
      if (prevProfiles.length !== newProfiles.length) {
        setBackgroundColor(getColor(newProfiles.length))
      }
    }
  })(),
)

console.log(state.backgroundColor) // 'white'

addProfile({ id: 0, name: 'george', gender: 'male' })
addProfile({ id: 1, name: 'sally', gender: 'female' })
addProfile({ id: 2, name: 'kelly', gender: 'female' })

console.log(state.backgroundColor) // 'white'

addProfile({ id: 3, name: 'mike', gender: 'male' })
addProfile({ id: 4, name: 'bob', gender: 'male' })

console.log(state.backgroundColor) // 'blue'

addProfile({ id: 5, name: 'kevin', gender: 'male' })
addProfile({ id: 6, name: 'henry', gender: 'male' })

console.log(state.backgroundColor) // 'blue'

addProfile({ name: 'ronald', gender: 'male' })
addProfile({ name: 'chris', gender: 'male' })
addProfile({ name: 'andy', gender: 'male' })
addProfile({ name: 'luke', gender: 'male' })

console.log(state.backgroundColor) // 'red'