PF 101 — Pre-final: For You

for-you.js

For You

Pre-final · Module 04 — why this post, not that one

PF 101 · New project Campus Feed Not Fighter Arena

New world

The arena is done. Put it away.

Midterm

You extended a starter. Warrior. Witch. attack(). Someone else wrote Game.

Pre-final

Blank js/. You type every class. The object is a post, not a fighter.

The hook

Your phone is not random

Something decided this video is worth more than your cousin’s photo. That something is a function with a name.

Stories scream, then vanish
Reels get paid for watch time
A photo with two likes can still lose to a dunk clip

The name

The function is called score()

Photo.score()  →  likes
Story.score()  →  likes × 3   (or 0 if 24h old)
Reel.score()   →  likes × 2 + seconds watched

feed.forYou()  →  sort by score()
                →  never asks the type

If Feed writes if (post is Reel), the magic is dead.

Map

Same pillars. New objects.

Content
  ├── Photo
  ├── Story      expires
  └── Reel       watch time

Creator     a name
Feed        HAS posts — composition, not extends

Four pillars

Where they hide in the feed

INHERIT

extends Content

Photo, Story, Reel reuse like() and caption.

POLY

score()

Same name. Three formulas. Feed calls one word.

ENCAP

#likes

You cannot cheat 999 likes. You call like().

Feel it

Canteen vs dunk vs expired crush

Post	Math	Score
Photo · 2 likes	2	2
Story · 3 likes · 30 hours old	expired	0
Story · 2 likes · 2 hours old	2 × 3	6
Reel · 1 like · 40s watched	2 + 40	42

The dunk wins. The crush story had more likes — and still lost. That is the algorithm.

Your island

Post what you actually scroll

Ferry cancelled — sleep in
Canteen sold out of siomai
Intramurals dunk from half court
Prof cancelled — story that dies tonight

Folder

The phone is empty until you type

campus-feed/

index.html phone frame only

css/feed.css

js/ you create every file

content.js

photo.js story.js reel.js

creator.js feed.js main.js

Not today

Leave these in midterm

✕Fighter, Game, attack(), health bars
✕Copy-paste from the starter
✕if (post instanceof Reel) inside Feed
✓Type every line. Know every line.

Close Fighter Arena. Open campus-feed. The For You page is yours.