js 判断网速大小

function testDownloadSpeed(url, fileSize) {
    return new Promise((resolve, reject) => {
        const startTime = Date.now();
        fetch(url)
            .then(response => response.blob())
            .then(() => {
                const endTime = Date.now();
                const duration = (endTime - startTime) / 1000; // in seconds
                const speed = (fileSize * 8) / duration; // in bits per second
                resolve(speed);
            })
            .catch(error => reject(error));
    });
}

// 使用示例
const testUrl = 'path/to/testfile'; // 替换为实际测试文件URL
const fileSizeInBytes = 500000; // 测试文件大小，单位字节
testDownloadSpeed(testUrl, fileSizeInBytes)
    .then(speed => console.log(`Download speed: ${speed / 1000000} Mbps`))
    .catch(error => console.error('Error testing download speed:', error));