Working with `BigNumber` in ethers.js: A Guide for Version 6

Handling large integers is a common need in blockchain development, especially when dealing with cryptocurrencies like Ethereum where numbers can get extremely large. ethers.js, a popular JavaScript library for interacting with the Ethereum blockchain, has long supported this functionality using BigNumber. In ethers.js version 6, BigNumber now comes from the bignumber.js library, which offers more robust and feature-rich capabilities for handling large integers.

In this section, we will walk through how to work with BigNumber in ethers.js version 6, including creating instances, performing arithmetic operations, comparisons, and conversions.

1. Importing BigNumber

To begin working with BigNumber, you need to import it from ethers.js:

const { BigNumber, utils } = require('ethers');

2. Creating BigNumber Instances

You can create BigNumber instances in several ways, including from numbers, strings, hexadecimal values, or even other BigNumber instances.

• From a Number:

  const num = BigNumber.from(12345);

• From a String:

  const num = BigNumber.from('12345');

• From a Hexadecimal String:

  const hexNum = BigNumber.from('0x12345');

• From Another BigNumber:

  const copyNum = BigNumber.fromValue(num);

3. Performing Arithmetic Operations

BigNumber supports a variety of arithmetic operations, including addition, subtraction, multiplication, and division. However, remember that BigNumber objects are immutable, meaning that every arithmetic operation returns a new instance.

• Addition:

  const result = num1.add(num2);

• Subtraction:

  const result = num1.sub(num2);

• Multiplication:

  const result = num1.mul(num2);

• Division:

  const result = num1.div(num2);

Example:

const num1 = BigNumber.from(10);
const num2 = BigNumber.from(5);

console.log(num1.add(num2).toString()); // "15"
console.log(num1.sub(num2).toString()); // "5"

4. Comparing BigNumbers

BigNumber instances can be compared using various methods such as eq (equals), lt (less than), and gt (greater than).

• Equality Check:

  console.log(num1.eq(num2)); // false

• Less Than:

  console.log(num1.lt(num2)); // false

• Greater Than:

  console.log(num1.gt(num2)); // true

5. Conversion and Formatting

You can convert a BigNumber instance into different formats such as hexadecimal, string, or a regular number. This is useful when you need to display values or perform further operations.

• To Hexadecimal:

  const hexString = num.toHexString(); // "0x3039"

• To Decimal String:

  const decimalString = num.toString(); // "12345"

• To Number:

  const numberValue = num.toNumber(); // 12345

6. Utility Functions in BigNumber

The ethers.js library provides various utility functions for working with BigNumber instances, including methods to format numbers, check if a number is negative, and other essential checks. For a full list of features, refer to the [ethers.js documentation](https://docs.ethers.io/v6).

Conclusion

BigNumber in ethers.js version 6 offers a powerful way to handle large numbers, ensuring that your Ethereum-related calculations are precise and secure. Whether you're adding large amounts of Ether, comparing transaction values, or converting numbers to different formats, BigNumber makes these operations seamless.

With this guide, you now have the tools to work with BigNumber in your ethers.js projects, ensuring accuracy in your blockchain calculations. Happy coding!