Any Unknown

// --- reassign across underlying types ---
let x: any = 5
console.log(x)              // 5
x = "hello"
console.log(x)              // hello
x = true
console.log(x)              // true
x = null
console.log(x)              // null

// --- template literals pick up the current runtime value ---
let msg: any = 42
console.log(`value: ${msg}`)  // value: 42
msg = "world"
console.log(`value: ${msg}`)  // value: world

// --- typeof is a real runtime check, not a compile-time constant ---
let dyn: any = 5
console.log(typeof dyn)     // number
dyn = "hi"
console.log(typeof dyn)     // string
dyn = true
console.log(typeof dyn)     // boolean
dyn = null
console.log(typeof dyn)     // object (the well-known JS quirk)

let uninitialized: any
console.log(typeof uninitialized)  // undefined

// --- unknown behaves the same as any at runtime ---
let u: unknown = 3.14
console.log(u)               // 3.14
console.log(typeof u)        // number

// --- equality ---
let a: any = 5
let b: any = 5
console.log(a === b)         // 1
let c: any = "5"
console.log(a === c)         // 0 (different underlying types, unlike loose JS ==)
console.log(a === 5)         // 1 (comparing against a plain literal also works)

let f: any = 5.0
console.log(a === f)         // 1 (5 === 5.0 numerically, matching JS number semantics)

// A concretely-typed closure behind an any-signature slot adapts at the
// boundary: returns box, parameters unbox, values survive intact.
const format: (n: number) => any = (n: number): string => "#" + String(n)
console.log(format(3))           // #3

class Mapper {
    map<U>(n: number, f: (n: number) => U): U { return f(n) }
}
console.log(new Mapper().map(6, (n: number): number => n * 7))  // 42

// Arrays and nullable scalars adapt too — an any-boxed array keeps its
// length (heap {ptr, len} header), so it unboxes back into a real array.
const dbl: (n: number) => number[] = (n: number): any => [n, n * 2]
const pair = dbl(3)
console.log(pair.length, pair[1])   // 2 6
const opt: (x: number | null) => any = (x: number | null): number | null => x
console.log(opt(9))                 // 9