Add symbol, undefined and null predicates

[SamVerschueren]

Completed all the primitive predicates by adding symbol, undefined and null.

[sindresorhus]

Let's put symbol after null as it's not as common to check for it.

[SamVerschueren]

Fixed.

I'm also thinking in refactoring the Object.defineProperties block to something like this.

const predicateMap = new Map<string, () => Predicate>([
	['string', () => new StringPredicate()],
	['number', () => new NumberPredicate()],
	['boolean', () => new BooleanPredicate()],
	['array', () => new ArrayPredicate()],
	['date', () => new DatePredicate()]
]);

for (const propertyKey of Array.from(predicateMap.keys())) {
	Object.defineProperty(main, propertyKey, {
		get: predicateMap.get(propertyKey)
	});
}

It feels easier to maintain.

[sindresorhus]

Could also be:

const predicateMap = new Map<string, Predicate>([
	['string', StringPredicate],
	['number', NumberPredicate],
	['boolean', BooleanPredicate],
	['array', ArrayPredicate],
	['date', DatePredicate]
]);

for (const propertyKey of Array.from(predicateMap.keys())) {
	Object.defineProperty(main, propertyKey, {
		get: () => new predicateMap.get(propertyKey)
	});
}

[sindresorhus]

But I don't think it's worth it. Now it's just a tiny bit more boilerplate, but much clearer.

[SamVerschueren]

But I don't think it's worth it. Now it's just a tiny bit more boilerplate, but much clearer.

True 👌