Handling large numbers in an interpreted language like Javascript can be tricky. Here are some tips for working with them more effectively.

Handing large numbers can be problematic in dynamic / scripting languages. In JS we use the bigint type.

const largeNumber: bigint = 2381023981203981203918320312039n;
const anotherLargeNumber: bigint = BigInt(
	"56666666666666666666666666666666667",
);

Note: The BigInt function also accepts number as input parameter. However, that would defeat the purpose of using bigint and that should be avoided.

Note: In case a very large number is required to be transmitted over-the-wire encoded in JSON, use string type to encode the number. This will ensure that number precision is not lost.

const rawData = `{ "number": "699999999999999999999999999999997" }`;
const parsed: { number: string } = JSON.parse(rawData);

const parsedNumber: bigint = BigInt(parsed.number);
console.log(parsedNumber.toString());

JSON and BigInt

One big limitation of bigint is that it cannot be encoded to json by default. One option is to override the toJSON method on BigInt.prototype.

BigInt.prototype.toJSON = function () {
	return this.toString();
};

The above option is not very typescript-friendly. Also, we need to ensure that this logic executes before anything else in our application, which can be a pain. Another option which may work better is as follows.

class BigNumber {
	public readonly value: bigint;

	constructor(value: string | bigint) {
		this.value = BigInt(value);
	}

	add(other: BigNumber): BigNumber {
		const result = this.value + other.value;
		return new BigNumber(result);
	}

	subtract(other: BigNumber): BigNumber {
		const result = this.value - other.value;
		return new BigNumber(result);
	}

	multiply(other: BigNumber): BigNumber {
		const result = this.value * other.value;
		return new BigNumber(result);
	}

	divide(other: BigNumber): BigNumber {
		const result = this.value / other.value;
		return new BigNumber(result);
	}

	toString(): string {
		return this.value.toString();
	}

	// this method is important because it will make our class JSON serializable.
	toJSON() {
		return this.value.toString();
	}
}