دمج typeof وkeyof

const colors = { red: "#f00", green: "#0f0" }
type ColorKey = keyof typeof colors // "red" | "green"
const k: ColorKey = "red"
console.log(colors[k])

const status = { active: 1, inactive: 0, pending: 2 }
type Status = keyof typeof status // "active" | "inactive" | "pending"
const s: Status = "pending"
console.log(status[s]) // 2

const rates = { usd: 1, eur: 1.1, gbp: 1.3 }
function rate(currency: keyof typeof rates): number {
  return rates[currency]
}
console.log(rate("eur")) // 1.1
// rate("jpy") // Error: not a key

const Direction = { Up: "UP", Down: "DOWN" } as const
type DirKey = keyof typeof Direction // "Up" | "Down"
type DirValue = typeof Direction[keyof typeof Direction] // "UP" | "DOWN"
console.log(Direction.Up)

const sizes = { sm: 8, md: 16, lg: 24 } as const
type SizeName = keyof typeof sizes // "sm" | "md" | "lg"
type SizeValue = typeof sizes[keyof typeof sizes] // 8 | 16 | 24
const v: SizeValue = 16
console.log(v)

function getProperty<T, K extends keyof T>(obj: T, key: K): T[K] {
  return obj[key]
}
const user = { id: 1, name: "Ada" }
const name = getProperty(user, "name") // string
console.log(name)

function getProperty<T, K extends keyof T>(obj: T, key: K): T[K] {
  return obj[key]
}
const u = { id: 1, name: "Ada" }
const id = getProperty(u, "id")     // number
const nm = getProperty(u, "name")   // string
console.log(id, nm)

function getProperty<T, K extends keyof T>(obj: T, key: K): T[K] {
  return obj[key]
}
const u = { id: 1 }
// getProperty(u, "missing") // Error: not a key of u
console.log(getProperty(u, "id"))

function setProperty<T, K extends keyof T>(obj: T, key: K, value: T[K]): void {
  obj[key] = value
}
const u = { id: 1, name: "Ada" }
setProperty(u, "name", "Leo")
console.log(u.name)

const theme = { primary: "#007", danger: "#f00" } as const
function color(name: keyof typeof theme): string {
  return theme[name]
}
console.log(color("danger")) // #f00