coerceBooleanProperty as property decorator

coerce-boolean.ts

function coerceBooleanProperty(prop: unknown): boolean {
    return !!prop;
}

const CoerceBoolean: PropertyDecorator = (proto, prop) => { 
    const values = new WeakMap();
    Object.defineProperty(proto, prop, {
        get() {
            return values.get(this)
        },
        set(value: unknown) {
            values.set(this, coerceBooleanProperty(value))
        },
        enumerable: true
    })
}

example.ts

class Example {
    @CoerceBoolean prop = false;

    get not() {
        return !this.prop;
    }
}

let ex = new Example;

console.log(ex, ex.prop);

(ex as any).prop = "lol";

console.log(ex, ex.prop);