Build a Real-Time Currency Converter

Building a currency converter is a classic project for developers. It's a practical way to learn the fundamentals of working with a third-party API: making an HTTP request, parsing a JSON response, and dynamically updating the UI.

This tutorial will walk you through building a clean, functional currency converter web application from scratch. We will use HTML, CSS, and vanilla JavaScript to call a REST API, fetch a live exchange rate, and perform the conversion instantly. We'll be using the Currency Exchange API for its simple endpoint and straightforward JSON response.

Step 1: Get Your API Key

Before you can make a request, you need an API key to authenticate.

Sign up for a free account at **https://www.juheapi.com/console**.

1. Navigate to your dashboard to find your API keys.
2. Generate a new key for this project and copy it.

Step 2: Understanding the API Request and Response

The API is designed for simplicity.

• The Request: You'll make a GET request with a few key query parameters:
  • key: Your API key.
  • base: The currency you are converting from (e.g., USD).
  • target: The currency you are converting to (e.g., EUR).
  • rate: The amount of the base currency to convert.
• The JSON Response: A successful call returns a JSON object. The most important parts are convert_result (the converted amount) . For this guide, we'll focus on the primary result. A successful response might look like this:

{
  "code": "200",
  "msg": "Success",
  "convert_result": {
    "base": "USD",
    "target": "CNY",
    "rate": 7.26
  },
  "time_update": {
    "time_unix": 1750959474,
    "time_utc": "2025-06-26T03: 17: 54Z",
    "time_zone": "UTC"
  }
}

**Step 3: Building the Application **

Conclusion & Next Steps

Ready to expand? Dive into the full API Documentation to see the complete list of supported currencies or explore other powerful Fintech APIs on juheapi.com.