Though the lack of support in IE, current Edge, and Safari, blocks that from client-side use for many.
There are several BigInt libraries out there that you could use, though obviously this is not as convenient and even if they wrap BigInt when available will be less efficient.
Latest Edge dev preview has supported it since the switch to Chromium. The Chromium-based Edge launches on Jan 15th, at which point Edge will support it.
There are several BigInt libraries out there that you could use, though obviously this is not as convenient and even if they wrap BigInt when available will be less efficient.