var data = // an ArrayBuffer
var niftiHeader = null,
    niftiImage = null,
    niftiExt = null;

if (nifti.isCompressed(data)) {
    data = nifti.decompress(data);
}

if (nifti.isNIFTI(data)) {
    niftiHeader = nifti.readHeader(data);
    console.log(niftiHeader.toFormattedString());
    niftiImage = nifti.readImage(niftiHeader, data);
    
    if (nifti.hasExtension(niftiHeader)) {
        niftiExt = nifti.readExtensionData(niftiHeader, data);
    }
}