Convert size in bytes to human readable format (JavaScript)

formatBytes.js

export function formatBytes(bytes, decimals = 2, format = 'KB') {
    if (bytes < 1) {
        return '0 B';
    }
    const k = format === 'kB' ? 1000 : 1024;
    const i = Math.floor(Math.log(bytes) / Math.log(k));
    const sizes = ['', 'K', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y'];
    const suffix = [format === 'kB' ? sizes[i].toLowerCase() : sizes[i], 'B'];
    if (format === 'KiB') {
        suffix.splice(1, 0, 'i');
    }
    return parseFloat((bytes / Math.pow(k, i)).toFixed(decimals)) + ' ' + suffix.join('');
}

// Usage:
// formatBytes(bytes,decimals, format)
// format can either be 'KiB', 'KB' or 'kB'. If you use 'kB', 1000 will be used to calculate size

formatBytes(1024);       // 1 KB
formatBytes('1024');     // 1 KB
formatBytes(1234);       // 1.21 KB
formatBytes(1234, 3);    // 1.205 KB