workshop - chain of fallbacks

[serapath]

Prototype Chain (= "chain of fallbacks") - How does it work in it's core?

1. "fallbacks" are a main pillar of JavaScript together with "callbacks" which is another one.
2. A lot of JavaScript syntax uses this core mechanism, for example: (new, .prototype, class, ...)
3. What is it all about?
   • If you look for a thing in a place and cant' find it
   • then go to the next place where you might find it and if you can't find it there
   • then go to the next place where you might find it and if you can't find it there
   • then go to the next place where you might find it and if you can't find it there
   • then go to the next place ...unless it's the end of the list of "fallback places" (that are used to look for stuff in case you couldnt find it)
4. How does it look in code?

var place = {}
var fallback_place1 = { A: 1, B: 2, C: 3,  foo: x => 'foo', D: 4 }
var fallback_place2 = { E: 1, F: 2, G: 3,  bar: x => 'bar', H: 4 }
var fallback_place3 = { I: 1, J: 2, K: 3,  baz: x => 'baz', L: 4 }
var fallback_place4 = { M: 1, N: 2, O: 3,  quux: x => 'quux', P: 4 }

// Set of the prototype chain (= "chain of fallbacks")
place.__proto__ = fallback_place1
fallback_place1.__proto__ = fallback_place2
fallback_place2.__proto__ = fallback_place3
fallback_place3.__proto__ = fallback_place4

// look for "quux"
console.log(place.quux()) // => 'quux'

Now when you learn about JavaScript Syntax like (class, .prototype, new, extends, Object.create, Object.setPrototypeOf`, ...), it essentially always comes back to the above.