globals-are-evil.md

Globals are evil

Some hints by Krzysztof Grzybek:

1. Global and static objects cause implicit dependencies/coupling, thus they break the idea of encapsulation.
2. It's hard to reason about them - logical scope for understanding behaviour of these objects is expanded to the whole program.
3. It's hard to mock/stub them.
4. Global objects pollute the main scope.

Bad:

class Player {
    walk() {
        this.x = nextDestination.x;
        this.y = nextDestination.y;
    }
}

Good:

class Player {
    walk(destination) {
        this.x = destination.x;
        this.y = destination.y;
    }
}