Code from video about Weak References, WeakSet, and WeakMap

main.js

const log = console.log;
//Strong Ref and Reachability - the default state
let person = { id: 123, name: 'Shaggy' };
let list = [person];
person = null; //destroys one reference
//person list[0]
// log(list);
// log(person);

//Set - unique list of values, any datatype, strong ref
//WeakSet - values must be objects, no loop, weak ref
let kids = new WeakSet();
let son = { name: 'Alex' };
let daughter = { name: 'Bree' };
kids.add(son);
kids.add(daughter);
// log('has son', kids.has(son));
// log('has daughter', kids.has(daughter));
son = null;
// log('has son', kids.has(son));
// log('has daughter', kids.has(daughter));

//Map - key value pairs, unique, keys are objs, remembers order
//WeakMap - no looping, weak ref

let theGang = new WeakMap();
let fred = { id: 123, gender: 'male' };
let daphne = { id: 456, gender: 'female' };
let velma = { id: 789, gender: 'female' };
theGang.set(fred, 'blue');
theGang.set(daphne, 'purple');
theGang.set(velma, 'orange');
log(theGang.has(fred));
log(theGang.has(daphne));
log(theGang.has(velma));
let scooby = fred;
daphne = null;
fred = null;
log(theGang.has(fred));
log(theGang.has(scooby));
log(theGang.has(daphne));
log(theGang.has(velma));