spi.send with Uint16Array

@Gordon,
I've added a function to read screendata. This data is given as 3 bytes for r/g/b.
Colourdata for writing is a word (5 bit for red, 6 bits for green and 5 for blue).
Reading data is done this way.

....    
sData = new Uint16Array(cnt);  //cnt is number of pixels to be read
writeCMD(0x2E);    //read memory command
    dc.write(1);
    spi.send(z);    //z is any value, this needs to be sent for unknown reason
    for(var i = 0; i < cnt; i++){ 
      r = spi.send(z)>>3;g = spi.send(z)>>2; b = spi.send(z)>>3; //read 3 bytes for 3 colours
      sData[i] = (r<<11) + (g<<5) + b;
    }
    ce.write(1);
    return sData;       

Data should have same format as for writing. I could switch upper and lower byte, thats correct. Any suggestion, how to do that ? May be a short assembler is best solution ?
BTW, reading data this way is very slow, any suggestion to do better ?