Function assertValidLevel

source/index.js:17–21

const styles = Object.create(null);

const assertValidLevel = level => {
	if (!Number.isSafeInteger(level) || level < 0 || level > 3) {
		throw new Error('The `level` should be an integer from 0 to 3');
	}
};

// The level is stored under a symbol so the hot path can read it as a plain property, while `level` itself is an accessor that rejects values the rest of the code could not handle.
const levelDescriptor = {