CODEWITHSUNDEEP
node.jstypescript
naddison
naddison

Reputation: 613

TypeScript Type Definitions for BigNumber

I'm trying to use BigNumber version 4.0.2 in a TypeScript program. I've created a stripped down example of a simple Node.js program written in TypeScript that uses BigNumber for this issue https://github.com/naddison36/node-imports

I'm really struggling to get TypeScript 2.3.4 to pull in the type definitions for BigNumber. Does anyone know how to do this? Here's what I've tried so far https://github.com/naddison36/node-imports#attempts-to-get-the-bignumber-type-definitions-to-work

Ideally I'd like to simply run npm install bignumber.js --save, npm install @types/bignumber.js --save, use ES6 imports like import BigNumber from 'bignumber.js' and have TypeScript just work.

Any help would be appreciated

Upvotes: 1

Views: 21798

Answers (2)

Catalyst
Catalyst

Reputation: 3247

The import style

import BigNumber from 'bignumber.js';

Only works if the library specified a default export, but as you note in the github repository.

Changing line 10 from export = BigNumber; to export default BigNumber; fixes the above error but introduces the following error:

Error:(6, 15) TS2709:Cannot use namespace 'BigNumber' as a type.

This is because the typings for bignumber.js are declared using namespace, instead of module. I'm not sure you can work around the typings as they are, but changing them so the beginning goes

export default BigNumber;
declare module 'bignumber.js' {
var BigNumber: BigNumberStatic;

instead of 

declare var BigNumber: BigNumber.BigNumberStatic;

export as namespace BigNumber;
export = BigNumber;

declare namespace BigNumber {

works fine for me in all the normal imports of bignumber.js

import * as b from 'bignumber.js'
new b.BigNumber(123)

import b from 'bignumber.js'
new b(123)

import {BigNumber} from 'bignumber.js'
new BigNumber(123)

Upvotes: 3

Saravana
Saravana

Reputation: 40604

So doing this seems to work:

import * as BigNumber from 'bignumber.js';
const result: BigNumber.BigNumber = new BigNumber(2);

Possible explanation:

The typings declare a variable and a namespace both named BigNumber:

declare var BigNumber: BigNumber.BigNumberStatic;
export as namespace BigNumber;

In the importing code, what you imported as * as BigNumber refers to the namespace whereas the one in new BigNumber refers to the variable declared.

Upvotes: 0

Related Questions