nodejs write binary data into WritableStream with Buffer - node.js

Question

The following code tries to write the header of a WAV file to a stream
using a Buffer and then writing it to a WritableStream.
var fs = require("fs")
var samplesLength = 1000;
var sampleRate = 44100;
var outStream = fs.createWriteStream("zaz.wav")
var b = new Buffer(1024)
b.write('RIFF', 0);
/* file length */
b.writeUInt32LE(32 + samplesLength * 2, 4);
//b.writeUint32LE(0, 4);
b.write('WAVE', 8);
/* format chunk identifier */
b.write('fmt ', 12);
/* format chunk length */
b.writeUInt32LE(16, 16);
/* sample format (raw) */
b.writeUInt16LE(1, 20);
/* channel count */
b.writeUInt16LE(2, 22);
/* sample rate */
b.writeUInt32LE(sampleRate, 24);
/* byte rate (sample rate * block align) */
b.writeUInt32LE(sampleRate * 4, 28);
/* block align (channel count * bytes per sample) */
b.writeUInt16LE(4, 32);
/* bits per sample */
b.writeUInt16LE(16, 34);
/* data chunk identifier */
b.write('data', 36);
/* data chunk length */
//b.writeUInt32LE(40, samplesLength * 2);
b.writeUInt32LE(40, 0);
outStream.write(b.slice(0,50))
outStream.end()
For some reason, the first 8 bytes of the file are wrong :
hexdump -C zaz.wav
00000000 28 00 00 00 f0 07 00 00 57 41 56 45 66 6d 74 20 |(.......WAVEfmt |
00000010 10 00 00 00 01 00 02 00 44 ac 00 00 10 b1 02 00 |........D.......|
00000020 04 00 10 00 64 61 74 61 80 5a 57 ac ef 04 00 00 |....data.ZW.....|
00000030 18 57 |.W|
The first line should be :
00000000 52 49 46 46 24 00 ff 7f 57 41 56 45 66 6d 74 20 |RIFF$...WAVEfmt |
Update :
this line is at fault :
b.writeUInt32LE(40, 0);
it needs to be :
b.writeUInt32LE(0, 40);

Answer 1

The first 8 bits are written by b.writeUInt32LE(40, 0);.
= write (int) 40 (= 0x28) in Little Endian at offset 0.
I don't know exactly what you want but this is the problem.