Read pcm file in node js to get raw data

The below code parses a sample pcm file

var dataFile = 'C:\\Users\\<user>\\Desktop\\small.pcm';
fs.readFile(dataFile, function(err, res) {
    if(err) {

        console.log('Error:', e.stack);

    }else{
    var ampData = [];
    var arrByte = Uint8Array.from(Buffer.from(res)); //Convert to byte array
    for(var i=0;i<arrByte.length;i=i+2){
        var val;
        var byteA = arrByte[i];
        var byteB = arrByte[i+1];
        var sign = byteA & (1 << 7);
        var x = (((byteA & 0xFF) << 8) | (byteB & 0xFF)); // convert to 16 bit signed int
        if (sign) { // if negative
                val = 0xFFFF0000 | x;  // fill in most significant bits with 1's
        }else{
          val = x;
        }
        ampData.push(val)
     }
    }
});

The pcm is single channel, signed 16bit, so its format is list of 2 byte. I want to know if this is the right way to extract raw amplitude data from the pcm file and store it in an array.

I need this to create a waveform graph of data values for the given length of the audio.

I got the reference to convert to signed 16 bit integer from here : Convert two bytes into signed 16 bit integer in JavaScript

Turns out that I needed to make it little endian byte ordering

 for(var i=0;i<arrByte.length;i=i+2){
        var byteA = arrByte[i];
        var byteB = arrByte[i+1];
        var sign = byteB & (1 << 7);
        var val = (((byteA & 0xFF) | (byteB & 0xFF) << 8)); // convert to 16 bit signed int
        if (sign) { // if negative
                val = 0xFFFF0000 | val;  // fill in most significant bits with 1's
        }
        ampData.push(val)
    }

Now, I got the correct shape of the waveform as expected.