The JavaScript universe is full of wires.
A nine-chapter walkthrough of the mental model behind JavaScript values, variables, equality, properties, mutation, and prototypes — adapted from Dan Abramov & Maggie Appleton's Just JavaScript. Every chapter opens with one interactive widget so you build the intuition by playing before you read a word of prose. A final capstone then puts the whole model to work — growing a web framework from a single request-to-response contract.
Mental Models
Why let b = a; a = 0 leaves b at its old value — and the spreadsheet bug your fast brain skips right past.
The JavaScript Universe
Values are things that float in space, not things inside your code. Nine types, two families, and the typeof operator that names them.
Values and Variables
Primitives are immutable; variables are wires that point at them. Why reaction[0] = 'l' never prints "likes".
Counting the Values · I
Studying the universe from the inside. undefined, null, booleans, and the floating-point numbers that get sparser as you leave zero.
Counting the Values · II
BigInts, strings, symbols — and the line that matters: literals summon primitives but create brand-new objects and functions.
06Equality of Values
Same-value, strict, and loose equality — and the two special numbers (NaN, -0) where === breaks the rule.
Properties
Properties are wires too — they just start from objects, not from your code. The rules the engine follows to answer obj.prop.
Mutation
How Sherlock and Watson both end up in Malibu — spooky action at a distance — and the two ways to fix it. Plus const vs let.
Prototypes
How an empty pizza can taste of pineapple. The __proto__ wire, the lookup chain, shadowing, and prototype pollution.