Lykn

The Prototype Chain

JavaScript objects have a hidden link to another object — their prototype. When you access a property that doesn’t exist on an object, JavaScript walks up the prototype chain until it finds the property or reaches null.

The Chain

(bind obj (obj :x 1))
;; obj → Object.prototype → null

(bind arr #a(1 2 3))
;; arr → Array.prototype → Object.prototype → null

This is why every object has .toString() even though you didn’t define it — it’s inherited from Object.prototype. Every array has .map() because it’s on Array.prototype.

Why It Matters

The prototype chain explains four things the reader has already encountered:

1. Object:keys returns only own properties — not inherited ones
2. for-in includes inherited properties — which is why it’s avoided
3. Class inheritance (Ch 20) — classes set up prototype chains
4. Built-in methods exist — toString, valueOf, hasOwnProperty live on Object.prototype

Object:create

For explicit prototype setting:

(bind parent (obj :greet (fn () (console:log "hello"))))
(bind child (Object:create parent))
(child:greet)  ;; → "hello" — inherited from parent

Surface Lykn prefers type/match and closures over prototype-based inheritance. The prototype chain is infrastructure that powers JavaScript underneath — understanding it helps debug, but you rarely manipulate it directly.