汇率转换计算器

使用 HTML5、CSS3、JavaScript 和可靠的汇率 API 开发一款功能全面的货币转换器。创建简洁直观的界面，突出显示输入字段和货币选择器。实现实时汇率，并通过时间戳指示数据的新鲜度。支持 170 多种全球货币，包括加密货币，并采用适当的符号和格式。维护包含时间戳和汇率信息的转换历史记录。允许用户收藏常用货币对，以便快速访问。生成可自定义日期范围的交互式历史汇率图表。使用缓存汇率实现离线功能，并清晰标示数据是否过时。添加内置计算器，以执行复杂转换和算术运算。为目标汇率创建提醒，并可选择启用通知。在可用时并排比较不同服务提供商的汇率。支持以多种格式（PDF、CSV、JSON）打印和导出转换结果。

Develop a comprehensive currency converter using HTML5, CSS3, JavaScript and a reliable Exchange Rate API. Create a clean, intuitive interface with prominent input fields and currency selectors. Implement real-time exchange rates with timestamp indicators showing data freshness. Support 170+ global currencies including crypto with appropriate symbols and formatting. Maintain a conversion history log with timestamps and rate information. Allow users to bookmark favorite currency pairs for quick access. Generate interactive historical rate charts with customizable date ranges. Implement offline functionality using cached exchange rates with clear staleness indicators. Add a built-in calculator for complex conversions and arithmetic operations. Create rate alerts for target exchange rates with optional notifications. Include side-by-side comparison of different provider rates when available. Support printing and exporting conversion results in multiple formats (PDF, CSV, JSON).