README.md

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 ofmaking a new API call.

Error Handling

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

• NetworkError: Thrown when there is a network problem and the request cannot be made.
• ServerError: Thrown when the service does not return a HTTP 200 response.
• DataError: 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 {
  ServerError,
  NetworkError,
  DataError,
  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) {
    if (error instanceof NetworkError) {
      console.error("Network problem:", error.message);
    } else if (error instanceof ServerError) {
      console.error("Backend problem:", error.message);
    } else if (error instanceof DataError) {
      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.