function getBigIntConstructor() {
		if (typeof window !== 'undefined') {
			return window['BigInt'] || null;
		}
		if (typeof global !== 'undefined') {
			return global['BigInt'] || null;
		}
		if (typeof self !== 'undefined') {
			return self['BigInt'] || null;
		}
		throw new Error('Can\'t search globals for BigInt!');
	}
Indirectly access the global BigInt constructor, it
allows browsers that doesn't support BigInt to run
the library without breaking due to "undefined BigInt"
errors.