Filesaver.js: how to write a blob containing binary data?

Solved:

After digging for a while found in different questions the bits and peaces i needed to put together a solution (not sure if is the best practice, but is working!)

First I had to treat every kind of input (string, number(positive integer), number(signed floating real) in differnet ways to match the format I need in the file.

*1: from here got the StingToArrayBuffer solution

//string to ArrayBuffer
function str2ab(str) {
  var buf = new ArrayBuffer(str.length); // 2 bytes for each char
  var bufView = new Uint8Array(buf);
  for (var i = 0, strLen = str.length; i < strLen; i++) {
    bufView[i] = str.charCodeAt(i);
  }
  var result = new Uint8Array(bufView.buffer);
  return result;
}

*2: From that answer got the numberToArrayBuffer solution, modified to my needs!

//.............number to ArratBuffer //*2
//integer To ArrayBuffer - 4 bits
function int2ArrBuf(value) {
  const view = new DataView(new ArrayBuffer(4))
  for (var index = 3; index >= 0; --index) {
    view.setUint8(index, value % 256)
    value = value >> 8;
  }
  var int = new Uint8Array(view.buffer);
  return int
}

//Reverse order
function Xint2ArrBuf(value) {
  const view = new DataView(new ArrayBuffer(4))
  for (var index = 0; index <= 3; ++index) {
    view.setUint8(index, value % 256)
    value = value >> 8;
  }
  var int = new Uint8Array(view.buffer);
  return int
}
//......................

//one bit long integer
function strsize(value) {
  const view = new DataView(new ArrayBuffer(1))
  
    view.setUint8(0, value % 256)
    value = value >> 8;
 
  var result= new Uint8Array(view.buffer);
  return result
}

*3: from this one, figure how to save the point coordinates

//point To ArrayBuffer - 3x 8 bits
function Pt2ArrBuf(x,y,z){
  var float32 = new Float32Array(3);
  float32[0] = x;
  float32[1] = y;
  float32[2] = z;

  var f = new Float64Array(float32);
  var pt = new Int8Array(f.buffer);  
  
  return pt;
}

*4: preparing the data sequence and concatenating the TypedArrays

//here I write the file the way i Need it to be...

const binaryData = [
    int2ArrBuf(9),
    strsize(8),
    str2ab('<POINTS>'),
    int2ArrBuf(3),
    Xint2ArrBuf(2),
    strsize(1),
    str2ab('A'),
    Pt2ArrBuf(10.5,10,10),
    Xint2ArrBuf(2),
    strsize(1),
    str2ab('B'),
    Pt2ArrBuf(-20,10,0.7),
    int2ArrBuf(10),
    strsize(9),
    str2ab('</POINTS>') 
  ];

//here I join the many TypedArrays into one...
const mergedInt8Array = new Int8Array(binaryData.map(typedArray => [...new Int8Array(typedArray.buffer)]).flat());
console.log(mergedInt8Array);

*5: Codepen from David

*6: Correction on the blob syntax

//*5:direct download via FileSaver.js
var SaveButton = document.getElementById('save');
SaveButton.addEventListener('click', function () {
  var filename = document.getElementById("name").value;
  filename += '.txt';
  var blob = new Blob([mergedInt8Array], { type: "application/octet-stream"}); //*6
  saveAs(blob, filename);
});

Here is the Codepen with the Solution. Thank You.