How to convert a BigNumber to a normal number in Typescript

In TypeScript, converting a BigNumber to a native number is commonly required when working with libraries such as bignumber.js or ethers.js that provide BigNumber types. These libraries are typically used for handling large integer operations in JavaScript that exceed the safe integer range of the Number type (i.e., -2^53 to 2^53).

To convert a BigNumber to a native number, the most common approach is to use methods provided by the library. Below, I'll demonstrate this conversion using the bignumber.js library as an example.

First, ensure that the bignumber.js library is installed in your project. If not, install it using npm:

bash
npm install bignumber.js

Then, in your TypeScript code, you can use it as follows:

typescript
import BigNumber from 'bignumber.js';

const bn = new BigNumber('12345678901234567890'); // Create a BigNumber instance
const num = bn.toNumber(); // Convert BigNumber to JavaScript native Number type

console.log(num); // Print the converted number

It's important to note that the .toNumber() method should only be used when you are certain that the BigNumber value falls within the safe integer range of JavaScript (i.e., -2^53 to 2^53). If the BigNumber value exceeds this range, using .toNumber() may result in precision loss or conversion errors.

If you need to handle numbers that exceed the safe integer range, it's recommended to continue using BigNumber or consider representing the number in another form, such as a string. This helps avoid introducing potential numerical errors in your application.

In summary, converting a BigNumber to a native number is a straightforward process, but it's important to be mindful of the value range and safety. In practical applications, understanding and correctly handling these large numbers is crucial for ensuring the accuracy and stability of your program.