Exchanger

This package provides functionality to fetch the exchange rates of different currencies using Yahoo Finance APIs.

Installation

Using npm:

npm install @tamtamchik/exchanger

Using yarn:

yarn add @tamtamchik/exchanger

Usage

Import Exchanger in your TypeScript file:

import { getExchangeRate } from '@tamtamchik/exchanger'

async function fetchRate () {
  try {
    const rate = await getExchangeRate('USD', 'EUR')
    console.log(`Exchange rate from USD to EUR: ${rate}`)
  } catch (error) {
    console.error(`Failed to fetch the exchange rate: ${error.message}`)
  }
}

fetchRate()

Caching

To improve performance and reduce the number of requests made to the API, you can use the built-in caching feature. By default, caching is disabled. You can enable and customize caching by passing an options object to the getExchangeRate function:

// Cache for 1 hour (3600000 milliseconds)
const rate = await getExchangeRate('USD', 'EUR', { cacheDurationMs: 3600000 }) 

Once a rate is fetched, it's stored in an in-memory cache. If you fetch the same rate within the specified caching duration, the cached rate is returned instead of making a new API call.

Error Handling

This package defines the following error classes for better error handling:

• FetchError: Thrown when there is a network problem and the request cannot be made.
• BackendError: Thrown when the service does not return a HTTP 200 response.
• MalformedError: Thrown when the service does not return the expected data structure.

Each error class extends the built-in Error class, so you can use instanceof to check the error type.

import { BackendError, FetchError, getExchangeRate, MalformedError } from '@tamtamchik/exchanger'

async function fetchRate () {
  try {
    const rate = await getExchangeRate('USD', 'EUR')
    console.log(`Exchange rate from USD to EUR: ${rate}`)
  } catch (error) {
    if (error instanceof FetchError) {
      console.error('Network problem:', error.message)
    } else if (error instanceof BackendError) {
      console.error('Backend problem:', error.message)
    } else if (error instanceof MalformedError) {
      console.error('Unexpected response data:', error.message)
    } else {
      console.error('Unknown error:', error.message)
    }
  }
}

fetchRate()

Contributing

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

License

Exchanger is MIT licensed.